High light transmission and scratch-resistant anti-reflective articles

ABSTRACT

Embodiments of articles with optical coatings are described herein. According to one embodiment, an article may comprise a substrate having a major surface, and an optical coating disposed on the major surface and forming an anti-reflective surface, the optical coating comprising an anti-reflective coating. The article may exhibit a maximum hardness of about 12 GPa or greater as measured on the anti-reflective surface by a Berkovich Indenter Hardness Test along an indentation depth of about 100 nm or greater. The article may exhibit a single side average light reflectance measured at the anti-reflective surface of about 8% or less over an optical wavelength regime in the range from about 400 nm to about 800 nm. The article may exhibit an average light transmission of about 90% or greater over an optical wavelength regime in the range from about 400 nm to about 800 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of priorityto U.S. application Ser. No. 15/264,765 filed on Sep. 14, 2016 and U.S.Provisional Application Ser. No. 62/218,241 filed on Sep. 14, 2015, thecontents of each of which are relied upon and incorporated herein byreference in their entireties.

BACKGROUND

The disclosure relates to durable and scratch resistant anti-reflectivearticles and methods for making the same, and more particularly toarticles with multi-layer anti-reflective coatings exhibiting abrasionresistance, scratch resistance, low reflectivity, and colorlesstransmittance and/or reflectance.

Cover articles are often used to protect critical devices withinelectronic products, to provide a user interface for input and/ordisplay, and/or many other functions. Such products include mobiledevices, such as smart phones, mp3 players and computer tablets. Coverarticles also include architectural articles, transportation articles(e.g., articles used in automotive applications, trains, aircraft, seacraft, etc.), appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof. These applications often demand scratch-resistance and strongoptical performance characteristics, in terms of maximum lighttransmittance and minimum reflectance. Furthermore, some coverapplications require that the color exhibited or perceived, inreflection and/or transmission, does not change appreciably as theviewing angle is changed. In display applications, this is because, ifthe color in reflection or transmission changes with viewing angle to anappreciable degree, the user of the product will perceive a change incolor or brightness of the display, which can diminish the perceivedquality of the display. In other applications, changes in color maynegatively impact the aesthetic requirements or other functionalrequirements.

The optical performance of cover articles can be improved by usingvarious anti-reflective coatings; however known anti-reflective coatingsare susceptible to wear or abrasion. Such abrasion can compromise anyoptical performance improvements achieved by the anti-reflectivecoating. For example, optical filters are often made from multilayercoatings having differing refractive indices and made from opticallytransparent dielectric material (e.g., oxides, nitrides, and fluorides).Most of the typical oxides used for such optical filters are wideband-gap materials, which do not have the requisite mechanicalproperties, such as hardness, for use in mobile devices, architecturalarticles, transportation articles or appliance articles. Nitrides anddiamond-like coatings may exhibit high hardness values but suchmaterials do not exhibit the transmittance needed for such applications.

Abrasion damage can include reciprocating sliding contact from counterface objects (e.g., fingers). In addition, abrasion damage can generateheat, which can degrade chemical bonds in the film materials and causeflaking and other types of damage to the cover glass. Since abrasiondamage is often experienced over a longer term than the single eventsthat cause scratches, the coating materials disposed experiencingabrasion damage can also oxidize, which further degrades the durabilityof the coating.

Known anti-reflective coatings are also susceptible to scratch damageand, often, even more susceptible to scratch damage than the underlyingsubstrates on which such coatings are disposed. In some instances, asignificant portion of such scratch damage includes microductilescratches, which typically include a single groove in a material havingextended length and with depths in the range from about 100 nm to about500 nm. Microductile scratches may be accompanied by other types ofvisible damage, such as sub-surface cracking, frictive cracking,chipping and/or wear. Evidence suggests that a majority of suchscratches and other visible damage is caused by sharp contact thatoccurs in a single contact event. Once a significant scratch appears onthe cover substrate, the appearance of the article is degraded since thescratch causes an increase in light scattering, which may causesignificant reduction in brightness, clarity and contrast of images onthe display. Significant scratches can also affect the accuracy andreliability of articles including touch sensitive displays. Single eventscratch damage can be contrasted with abrasion damage. Single eventscratch damage is not caused by multiple contact events, such asreciprocating sliding contact from hard counter face objects (e.g.,sand, gravel and sandpaper), nor does it typically generate heat, whichcan degrade chemical bonds in the film materials and cause flaking andother types of damage. In addition, single event scratching typicallydoes not cause oxidization or involve the same conditions that causeabrasion damage and therefore, the solutions often utilized to preventabrasion damage may not also prevent scratches. Moreover, known scratchand abrasion damage solutions often compromise the optical properties.

Accordingly, there is a need for new cover articles, and methods fortheir manufacture, which are abrasion resistant, scratch resistant andhave improved optical performance.

SUMMARY

Embodiments of durable and scratch resistant anti-reflective articlesare described. In one or more embodiments, the article includes asubstrate and an optical coating disposed on the major surface formingan anti-reflective surface. In one or more embodiments, the opticalcoating includes an anti-reflective coating.

The article exhibits scratch resistance by exhibiting a maximum hardnessof about 12 GPa or greater, as measured by a Berkovich Indenter HardnessTest, as described herein, along an indentation depth of about 50 nm orgreater (e.g., about 100 nm or greater, from about 50 nm to about 300nm, from about 50 nm to about 400 nm, from about 50 nm to about 500 nm,from about 50 nm to about 600 nm, from about 50 nm to about 1000 nm orfrom about 50 nm to about 2000 nm), on the anti-reflective surface.

The article exhibits an abrasion resistance as measured on theanti-reflective surface after a 500-cycle abrasion using a Taber Test,as described herein. In one or more embodiments, the article exhibits anabrasion resistance (as measured on the anti-reflective surface)comprising about 1% haze or less, as measured using a hazemeter havingan aperture, wherein the aperture has a diameter of about 8 mm. In oneor more embodiments, the article exhibits an abrasion resistance (asmeasured on the anti-reflective surface) comprising an average roughnessRa, as measured by atomic force microscopy, of about 12 nm or less. Inone or more embodiments, the article exhibits an abrasion resistance (asmeasured on the anti-reflective surface) comprising a scattered lightintensity of about 0.05 (in units of 1/steradian) or less, at a polarscattering angle of about 40 degrees or less, as measured at normalincidence in transmission using an imaging sphere for scattermeasurements, with a 2 mm aperture at 600 nm wavelength. In someinstances, the article exhibits an abrasion resistance (as measured onthe anti-reflective surface) comprising a scattered light intensity ofabout 0.1 (in units of 1/steradian) or less, at a polar scattering angleof about 20 degrees or less, as measured at normal incidence intransmission using an imaging sphere for scatter measurements, with a 2mm aperture at 600 nm wavelength.

The article of one or more embodiments exhibits superior opticalperformance in terms of light transmittance and/or light reflectance. Inone or more embodiments, the article exhibits an average lighttransmittance (measured on the anti-reflective surface only) of about92% or greater (e.g., about 98% or greater) over an optical wavelengthregime (e.g., in the range from about 400 nm to about 800 nm or fromabout 450 nm to about 650 nm). In some embodiments, the article exhibitsan average light reflectance (measured at the anti-reflective surfaceonly) of about 2% or less (e.g., about 1% or less) over the opticalwavelength regime. The article may exhibits an average lighttransmittance or average light reflectance having an average oscillationamplitude of about 1 percentage points or less over the opticalwavelength regime. In one or more embodiments, the article exhibits anaverage photopic reflectance of about 1% or less at normal incidence, asmeasured on only the anti-reflective surface. In some embodiments, thearticle exhibits a single-side average photopic reflectance, measured atnormal or near-normal incidence (e.g. 0-10 degrees) on theanti-reflective surface only of less than about 10%. In someembodiments, the single-side average photopic reflectance is about 9% orless, about 8% or less, about 7% or less, about 6% or less, about 5% orless, about 4% or less, about 3%, or about 2% or less.

In some instances, the article exhibits an angular color shift (asdescribed herein) of less than about 10 (e.g., 5 or less, 4 or less, 3or less, 2 or less or about 1 or less) from a reference illuminationangle to an incident illumination angle in the range from about 2degrees to about 60 degrees, when viewed at the anti-reflective surfaceusing an illuminant. Exemplary illuminants include any one of CIE F2,CIE F10, CIE F11, CIE F12 and CIE D65. In one or more embodiment, thearticle may exhibit a b* value of less than about 2 in the CIE L*, a*,b* colorimetry system at all incidence illumination angles in the rangefrom about 0 to about 60 degrees. Alternatively or additionally, thearticle of some embodiments exhibits a transmittance color (ortransmittance color coordinates) and/or a reflectance color (orreflectance color coordinates) measured at the anti-reflective surfaceat normal incidence having a reference point color shift of less thanabout 2 from a reference point, as defined herein. In one or moreembodiments, the reference point may be the origin (0, 0) in the L*a*b*color space (or the color coordinates a*=0, b*=0 or a*=−2, b*=−2) or thetransmittance or reflectance color coordinates of the substrate. Theangular color shift, the reference point color shift and the colorcoordinates (a* and/or b*) described herein are observed under a D65and/or F2 illuminant. In some embodiments, the optical performancedescribed herein is observed under a F2 illuminant, which is known to bemore challenging due to the sharp spectral features of the F2 illuminantsource.

In one or more embodiments, the anti-reflective coating may include aplurality of layers. For example, in some embodiments, theanti-reflective coating includes a period comprising a first low RIlayer and a second high RI layer. The period may include a first low RIlayer and a second high RI disposed on the first low RI layer or viceversa. In some embodiments, the period may include a third layer. Theanti-reflective coating may include a plurality of periods such that thefirst low RI layer and the second high RI layer alternate. Theanti-reflective coating can include up to about 10 or 20 periods.

In some embodiments, the optical coating includes a scratch resistantlayer. Where scratch resistant layers are included, such layers may bedisposed on the anti-reflective coating. In other embodiments, thescratch resistant coating is disposed between the anti-reflectivecoating and the substrate. Exemplary scratch resistant layers mayexhibit a maximum hardness in the range from about 8 GPa to about 50 GPaas measured by a Berkovitch Indenter Hardness Test, as defined herein.

The scratch resistant layer may be disposed between the substrate andthe anti-reflective coating. In some embodiments, the anti-reflectivecoating may include a first portion and a second portion such that thescratch resistant layer is disposed between the first portion and thesecond portion. The thickness of the scratch-resistant layer may be inthe range from about 200 nanometers to about 3 micrometers.

In some embodiments, the article may include a layer having a refractiveindex greater than about 1.8. Materials that may be utilized in thatlayer include SiN_(x), SiO_(x)N_(y), Si_(u)Al_(y)O_(x)N_(y), AlN_(x),AlO_(x)N_(y) or a combination thereof.

In some instances, the article may include an additional layer, such asan easy-to-clean coating, a diamond-like carbon (“DLC”) coating, ascratch-resistant coating or a combination thereof. Such coatings may bedisposed on the anti-reflective coating or between layers of theanti-reflective coating.

The substrate utilized in one or more embodiments of the article caninclude an amorphous substrate or a crystalline substrate. An of anamorphous substrate includes glass that may be selected from the groupconsisting of soda lime glass, alkali aluminosilicate glass, alkalicontaining borosilicate glass and alkali aluminoborosilicate glass. Insome embodiments, the glass may be strengthened and may include acompressive stress (CS) layer with a surface CS of at least 250 MPaextending within the strengthened glass from a surface of the chemicallystrengthened glass to a depth of layer (DOL) of at least about 10 μm.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary, and areintended to provide an overview or framework to understanding the natureand character of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiment(s), and together with the description serve to explainprinciples and operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an article, according to one or moreembodiments;

FIG. 2 is a side view of an article, according to one or more specificembodiments;

FIG. 3 is a side view of an article, according to one or moreembodiments;

FIG. 4 is a side view of an article, according to one or moreembodiments;

FIG. 5 is a side view of an article, according to one or moreembodiments;

FIG. 6 is a side view of an article, according to one or moreembodiments;

FIG. 7 is a side view of an article, according to one or moreembodiments;

FIG. 8 is a side view of an article, according to one or moreembodiments;

FIG. 9 is a graph illustrating the hardness measurements as a functionof indentation depth and coating thickness;

FIG. 10 is a reflectance spectra of Modeled Example 1, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 11 depicts the reflected color of the article of Example 1 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 12 is a reflectance spectra of Modeled Example 2, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 13 depicts the reflected color of the article of Example 2 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 14 is a reflectance spectra of Modeled Example 3, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 15 depicts the reflected color of the article of Example 3 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 16 is a reflectance spectra of Modeled Example 4, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 17 depicts the reflected color of the article of Example 4 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 18 is a reflectance spectra of Modeled Example 5, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 19 depicts the reflected color of the article of Example 5 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 20 is a reflectance spectra of Modeled Example 6, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 21 depicts the reflected color of the article of Example 6 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 22 is a reflectance spectra of Modeled Example 7, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 23 depicts the reflected color of the article of Example 7 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 24 is a reflectance spectra of Modeled Example 8, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 25 depicts the reflected color of the article of Example 8 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 26 is a reflectance spectra of Modeled Example 9, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 27 depicts the reflected color of the article of Example 9 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 28 is a reflectance spectra of Modeled Example 10, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 29 depicts the reflected color of the article of Example 10 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 30 is a reflectance spectra of Modeled Example 11, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 31 depicts the reflected color of the article of Example 11 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 32 is a reflectance spectra of Modeled Example 12, calculated fromthe anti-reflective surface only, at different viewing angles;

FIG. 33 depicts the reflected color of the article of Example 12 showingthe reflected color under different illuminants at different viewingangles from 0° to 60°;

FIG. 34 depicts hardness of one or more coated glass articles describedherein;

FIG. 35 depicts light transmittance of one or more coated articlesdescribed herein;

FIG. 36 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 37 depicts light transmittance of one or more coated articlesdescribed herein;

FIG. 38 depicts light transmittance of one or more coated articlesdescribed herein;

FIG. 39 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 40 depicts reflectance color of one or more coated articlesdescribed herein;

FIG. 41 depicts reflectance color of one or more coated articlesdescribed herein;

FIG. 42 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 43 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 44 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 45 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 46 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 47 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 48 depicts hardness of one or more coated articles describedherein;

FIG. 49 depicts light reflectance of one or more coated articlesdescribed herein;

FIG. 50 depicts light transmittance of one or more coated articlesdescribed herein;

FIG. 51 depicts light transmittance of one or more coated articlesdescribed herein;

FIG. 52 depicts reflectance color of one or more coated articlesdescribed herein;

FIG. 53 depicts transmitted color of one or more coated articlesdescribed herein;

FIG. 54A is a plan view of an exemplary electronic device incorporatingany of the articles disclosed herein; and

FIG. 54B is a perspective view of the exemplary electronic device ofFIG. 54A.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings.

Referring to FIG. 1, the article 100 according to one or moreembodiments may include a substrate 110, and an optical coating 120disposed on the substrate. The substrate 110 includes opposing majorsurfaces 112, 114 and opposing minor surfaces 116, 118. The opticalcoating 120 is shown in FIG. 1 as being disposed on a first opposingmajor surface 112; however, the optical coating 120 may be disposed onthe second opposing major surface 114 and/or one or both of the opposingminor surfaces, in addition to or instead of being disposed on the firstopposing major surface 112. The optical coating 120 forms ananti-reflective surface 122.

The optical coating 120 includes at least one layer of at least onematerial. The term “layer” may include a single layer or may include oneor more sub-layers. Such sub-layers may be in direct contact with oneanother. The sub-layers may be formed from the same material or two ormore different materials. In one or more alternative embodiments, suchsub-layers may have intervening layers of different materials disposedtherebetween. In one or more embodiments a layer may include one or morecontiguous and uninterrupted layers and/or one or more discontinuous andinterrupted layers (i.e., a layer having different materials formedadjacent to one another). A layer or sub-layers may be formed by anyknown method in the art, including discrete deposition or continuousdeposition processes. In one or more embodiments, the layer may beformed using only continuous deposition processes, or, alternatively,only discrete deposition processes.

The thickness of the optical coating 120 may be about 1 μm or greaterwhile still providing an article that exhibits the optical performancedescribed herein. In some examples, the optical coating 120 thicknessmay be in the range from about 1 μm to about 20 μm (e.g., from about 1μm to about 10 μm, or from about 1 μm to about 5 μm).

As used herein, the term “dispose” includes coating, depositing and/orforming a material onto a surface using any known method in the art. Thedisposed material may constitute a layer, as defined herein. The phrase“disposed on” includes the instance of forming a material onto a surfacesuch that the material is in direct contact with the surface and alsoincludes the instance where the material is formed on a surface, withone or more intervening material(s) is between the disposed material andthe surface. The intervening material(s) may constitute a layer, asdefined herein.

As shown in FIG. 2, the optical coating 120 includes an anti-reflectivecoating 130, which may include a plurality of layers (130A, 130B). Inone or more embodiments, the anti-reflective coating 130 may include aperiod 132 comprising two or more layers. In one or more embodiments,the two or more layers may be characterized as having differentrefractive indices from each another. In one embodiment, the period 132includes a first low RI layer 130A and a second high RI layer 130B. Thedifference in the refractive index of the first low RI layer and thesecond high RI layer may be about 0.01 or greater, 0.05 or greater, 0.1or greater or even 0.2 or greater.

As shown in FIG. 2, the anti-reflective coating 130 may include aplurality of periods (132). A single period includes include a first lowRI layer 130A and a second high RI layer 130B, such that when aplurality of periods are provided, the first low RI layer 130A(designated for illustration as “L”) and the second high RI layer 130B(designated for illustration as “H”) alternate in the following sequenceof layers: L/H/L/H or H/L/H/L, such that the first low RI layer and thesecond high RI layer appear to alternate along the physical thickness ofthe anti-reflective coating 120. In the example in FIG. 2, theanti-reflective coating 130 includes three periods. In some embodiments,the anti-reflective coating 130 may include up to 25 periods. Forexample, the anti-reflective coating 130 may include from about 2 toabout 20 periods, from about 2 to about 15 periods, from about 2 toabout 10 periods, from about 2 to about 12 periods, from about 3 toabout 8 periods, from about 3 to about 6 periods.

In the embodiment shown in FIG. 3, the anti-reflective coating 130 mayinclude an additional capping layer 131, which may include a lowerrefractive index material than the second high RI layer 130B. In someembodiments, the period 132 may include one or more third layers 130C,as shown in FIG. 3. The third layer(s) 130C may have a low RI, a high RIor a medium RI. In some embodiments, the third layer(s) 130C may havethe same RI as the first low RI layer 130A or the second high RI layer130B. In other embodiments, the third layer(s) 130C may have a medium RIthat is between the RI of the first low RI layer 130A and the RI of thesecond high RI layer 130B. Alternatively, the third layer(s) 130C mayhave a refractive index greater than the 2^(nd) high RI layer 130B. Thethird layer may be provided in the anti-reflective coating 120 in thefollowing exemplary configurations: L_(third layer)/H/L/H/L;H_(third layer)/L/H/L/H; L/H/L/H/L_(third layer);H/L/H/L/H_(third layer); L_(third layer)/H/L/H/L/H_(third layer);H_(third layer)/L/H/L/H/L_(third layer); L_(third layer)/L/H/L/H;H_(third layer)/H/L/H/L; H/L/H/L/L_(third layer);L/H/L/H/H_(third layer); L_(third layer)/L/H/L/H/H_(third layer);H_(third layer)//H/L/H/L/L_(third layer); L/M_(third layer)/H/L/M/H;H/M/L/H/M/L; M/L/H/L/M; and other combinations. In these configurations,“L” without any subscript refers to the first low RI layer and “H”without any subscript refers to the second high RI layer. Reference to“L_(third sub-layer)” refers to a third layer having a low RI,“H_(third sub-layer)” refers to a third layer having a high RI and “M”refers to a third layer having a medium RI, all relative to the 1^(st)layer and the 2^(nd) layer.

As used herein, the terms “low RI”, “high RI” and “medium RI” refer tothe relative values for the RI to another (e.g., low RI<medium RI<highRI). In one or more embodiments, the term “low RI” when used with thefirst low RI layer or with the third layer, includes a range from about1.3 to about 1.7 or 1.75. In one or more embodiments, the term “high RI”when used with the second high RI layer or with the third layer,includes a range from about 1.7 to about 2.5 (e.g., about 1.85 orgreater). In some embodiments, the term “medium RI” when used with thethird layer, includes a range from about 1.55 to about 1.8. In someinstances, the ranges for low RI, high RI and medium RI may overlap;however, in most instances, the layers of the anti-reflective coating130 have the general relationship regarding RI of: low RI<medium RI<highRI.

The third layer(s) 130C may be provided as a separate layer from aperiod 132 and may be disposed between the period or plurality ofperiods and the capping layer 131, as shown in FIG. 4. The thirdlayer(s) may also be provided as a separate layer from a period 132 andmay have disposed between the substrate 110 and the plurality of periods132, as shown in FIG. 5. The third layer(s) 130C may be used in additionto an additional coating 140 instead of the capping 131 or in additionto the capping layer, as shown in FIG. 6.

Exemplary materials suitable for use in the anti-reflective coating 130include: SiO₂, Al₂O₃, GeO₂, SiO, AlOxNy, AlN, SiNx, SiO_(x)N_(y),Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, TiO₂, ZrO₂, TiN, MgO, MgF₂, BaF₂,CaF₂, SnO₂, HfO₂, Y₂O₃, MoO₃, DyF₃, YbF₃, YF₃, CeF₃, polymers,fluoropolymers, plasma-polymerized polymers, siloxane polymers,silsesquioxanes, polyimides, fluorinated polyimides, polyetherimide,polyethersulfone, polyphenylsulfone, polycarbonate, polyethyleneterephthalate, polyethylene naphthalate, acrylic polymers, urethanepolymers, polymethylmethacrylate, other materials cited below assuitable for use in a scratch-resistant layer, and other materials knownin the art. Some examples of suitable materials for use in the first lowRI layer include SiO₂, Al₂O₃, GeO₂, SiO, AlO_(x)N_(y), SiO_(x)N_(y),Si_(u)Al_(v)O_(x)N_(y), MgO, MgAl₂O₄, MgF₂, BaF₂, CaF₂, DyF₃, YbF₃, YF₃,and CeF₃. The nitrogen content of the materials for use in the first lowRI layer may be minimized (e.g., in materials such as Al₂O₃ andMgAl₂O₄). Some examples of suitable materials for use in the second highRI layer include Si_(u)Al_(v)O_(x)N_(y), Ta₂O₅, Nb₂O₅, AlN, Si₃N₄,AlO_(x)N_(y), SiO_(x)N_(y), SiN_(x), SiN_(x):H_(y), HfO₂, TiO₂, ZrO₂,Y₂O₃, Al₂O₃, MoO₃ and diamond-like carbon. In examples, the high RIlayer may also be a high hardness layer or a scratch resistant layer,and the high RI materials listed above may also comprise high hardnessor scratch resistance. The oxygen content of the materials for thesecond high RI layer and/or the scratch-resistant layer may beminimized, especially in SiNx or AlNx materials. AlO_(x)N_(y) materialsmay be considered to be oxygen-doped AlNx, that is they may have an AlNxcrystal structure (e.g. wurtzite) and need not have an AlON crystalstructure. Exemplary preferred AlO_(x)N_(y) high RI materials maycomprise from about 0 atom % to about 20 atom % oxygen, or from about 5atom % to about 15 atom % oxygen, while including 30 atom % to about 50atom % nitrogen. Exemplary preferred Si_(u)Al_(v)O_(x)N_(y) high RImaterials may comprise from about 10 atom % to about 30 atom % or fromabout 15 atom % to about 25 atom % silicon, from about 20 atom % toabout 40 atom % or from about 25 atom % to about 35 atom % aluminum,from about 0 atom % to about 20 atom % or from about 1 atom % to about20 atom % oxygen, and from about 30 atom % to about 50 atom % nitrogen.The foregoing materials may be hydrogenated up to about 30% by weight.Where a material having a medium refractive index is desired, someembodiments may utilize AlN and/or SiO_(x)N_(y). The hardness of thesecond high RI layer and/or the scratch-resistant layer may becharacterized specifically. In some embodiments, the maximum hardness ofthe second high RI layer and/or the scratch-resistant layer, as measuredby the Berkovitch Indenter Hardness Test, may be about 8 GPa or greater,about 10 GPa or greater, about 12 GPa or greater, about 15 GPa orgreater, about 18 GPa or greater, or about 20 GPa or greater. In somecases, the second high RI layer material may be deposited as a singlelayer and may be characterized as a scratch resistant layer, and thissingle layer may have a thickness between about 500 and 2000 nm forrepeatable hardness determination.

In one or more embodiments at least one of the layer(s) of theanti-reflective coating 130 may include a specific optical thicknessrange. As used herein, the term “optical thickness” is determined by(n*d), where “n” refers to the RI of the sub-layer and “d” refers to thephysical thickness of the layer. In one or more embodiments, at leastone of the layers of the anti-reflective coating 130 may include anoptical thickness in the range from about 2 nm to about 200 nm, fromabout 10 nm to about 100 nm, from about 15 nm to about 100 nm, fromabout 15 to about 500 nm, or from about 15 to about 5000 nm. In someembodiments, all of the layers in the anti-reflective coating 130 mayeach have an optical thickness in the range from about 2 nm to about 200nm, from about 10 nm to about 100 nm, from about 15 nm to about 100 nm,from about 15 to about 500 nm, or from about 15 to about 5000 nm. Insome cases, at least one layer of the anti-reflective coating 130 has anoptical thickness of about 50 nm or greater. In some cases, each of thefirst low RI layers have an optical thickness in the range from about 2nm to about 200 nm, from about 10 nm to about 100 nm, from about 15 nmto about 100 nm, from about 15 to about 500 nm, or from about 15 toabout 5000 nm. In other cases, each of the second high RI layers have anoptical thickness in the range from about 2 nm to about 200 nm, fromabout 10 nm to about 100 nm, from about 15 nm to about 100 nm, fromabout 15 to about 500 nm, or from about 15 to about 5000 nm. In yetother cases, each of the third layers have an optical thickness in therange from about 2 nm to about 200 nm, from about 10 nm to about 100 nm,from about 15 nm to about 100 nm, from about 15 to about 500 nm, or fromabout 15 to about 5000 nm.

In some embodiments, the thickness of one or more of the layers of theoptical coating 130 may be minimized. In one or more embodiments, thethickness of the thickness of the high RI layer(s) and/or the medium RIlayer(s) are minimized such that they are less than about 500 nm. In oneor more embodiments, the combined thickness of the high RI layer(s), themedium RI (layers) and/or the combination of the high RI and medium RIlayers is less than about 500 nm.

In some embodiments, the amount of low RI material in the opticalcoating may be minimized. Without being bound by theory, the low RImaterial is typically also a lower-hardness material, owing to thenature of atomic bonding and electron densities that simultaneouslyaffect refractive index and hardness, and thus minimizing such materialcan maximize the hardness, while maintaining the reflectance and colorperformance described herein. Expressed as a fraction of physicalthickness of the optical coating, the low RI material may comprise lessthan about 60%, less than about 50%, less than about 40%, less thanabout 30%, less than about 20%, less than about 10%, or less than about5% of the physical thickness of the optical coating. Alternately oradditionally, the amount of low RI material may be quantified as the sumof the physical thicknesses of all layer of low RI material that aredisposed above the thickest high RI layer in the optical coating (i.e.on the side opposite the substrate, user side or air side). Withoutbeing bound by theory, the thick high RI layer having a high hardnesseffectively shields the layers underneath (or between the thick RI layerand the substrate) from many or most scratches. Accordingly, the layersdisposed above the thickest high RI layer may have an outsized effect onscratch resistance of the overall article. This is especially relevantwhen the thickest high RI layer has a physical thickness that is greaterthan about 400 nm and has a hardness greater than about 12 GPa asmeasured by the Berkovich Indenter Hardness Test. The amount of low RImaterial disposed on the thickest high RI layer (i.e. on the sideopposite the substrate, user side or air side) may have a thickness lessthan or equal to about 150 nm, less than or equal to about 120 nm, lessthan or equal to about 110 nm, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50nm, 40 nm, 30 nm, 25 nm, 20 nm, 15 nm, or less than or equal to about 12nm.

In some embodiments, the top-most air-side layer may comprise a high RIlayer that also exhibits high hardness, as shown in Modeled Examples8-9. In some embodiments, an additional coating 140 may be disposed ontop of this top-most air-side high RI layer (e.g., the additionalcoating may include low-friction coating, an oleophobic coating, or aneasy-to-clean coating). Moreover, as illustrated by Modeled Example 10,the addition of a low RI layer having a very low thickness (e.g., about10 nm or less, about 5 nm or less or about 2 nm or less) has minimalinfluence on the optical performance, when added to the top-mostair-side layer comprising a high RI layer. The low RI layer having avery low thickness may include SiO₂, an oleophobic or low-frictionlayer, or a combination of SiO₂ and an oleophobic material. Exemplarylow-friction layers may include diamond-like carbon, such materials (orone or more layers of the optical coating) may exhibit a coefficient offriction less than 0.4, less than 0.3, less than 0.2, or even less than0.1.

In one or more embodiments, the anti-reflective coating 130 has aphysical thickness of about 800 nm or less. The anti-reflective coating130 may have a physical thickness in the range from about 10 nm to about800 nm, from about 50 nm to about 800 nm, from about 100 nm to about 800nm, from about 150 nm to about 800 nm, from about 200 nm to about 800nm, from about 10 nm to about 750 nm, from about 10 nm to about 700 nm,from about 10 nm to about 650 nm, from about 10 nm to about 600 nm, fromabout 10 nm to about 550 nm, from about 10 nm to about 500 nm, fromabout 10 nm to about 450 nm, from about 10 nm to about 400 nm, fromabout 10 nm to about 350 nm, from about 10 nm to about 300 nm, fromabout 50 to about 300, and all ranges and sub-ranges therebetween.

In one or more embodiments, the combined physical thickness of thesecond high RI layer(s) may be characterized. For example, in someembodiments, the combined thickness of the second high RI layer(s) maybe about 100 nm or greater, about 150 nm or greater, about 200 nm orgreater, about 500 nm or greater. The combined thickness is thecalculated combination of the thicknesses of the individual high RIlayer(s) in the anti-reflective coating 130, even when there areintervening low RI layer(s) or other layer(s). In some embodiments, thecombined physical thickness of the second high RI layer(s), which mayalso comprise a high-hardness material (e.g., a nitride or an oxynitridematerial), may be greater than 30% of the total physical thickness ofthe anti-reflective coating. For example, the combined physicalthickness of the second high RI layer(s) may be about 40% or greater,about 50% or greater, about 60% or greater, about 70% or greater, about75% or greater, or even about 80% or greater, of the total physicalthickness of the anti-reflective coating. Additionally or alternatively,the amount of the high refractive index material, which may also be ahigh-hardness material, included in the optical coating may becharacterized as a percentage of the physical thickness of the uppermost (i.e., user side or side of the optical coating opposite thesubstrate) 500 nm of the article or optical coating 120. Expressed as apercentage of the upper most 500 nm of the article or optical coating,the combined physical thickness of the second high RI layer(s) (or thethickness of the high refractive index material) may be about 50% orgreater, about 60% or greater, about 70% or greater, about 80% orgreater, or even about 90% or greater. In some embodiments, greaterproportions of hard and high-index material within the anti-reflectivecoating can also simultaneously be made to also exhibit low reflectance,low color, and high abrasion resistance as further described elsewhereherein. In one or more embodiments, the second high RI layers mayinclude a material having a refractive index greater than about 1.85 andthe first low RI layers may include a material having a refractive indexless than about 1.75. In some embodiments, the second high RI layers mayinclude a nitride or an oxynitride material. In some instances, thecombined thickness of all the first low RI layers in the optical coating(or in the layers that are disposed on the thickest second high RI layerof the optical coating) may be about 200 nm or less (e.g., about 150 nmor less, about 100 nm or less, about 75 nm or less, or about 50 nm orless).

In some embodiments, the anti-reflective coating 130 exhibits an averagelight reflectance of about 9% or less, about 8% or less, about 7% orless, about 6% or less, about 5% or less, about 4% or less, about 3% orless, or about 2% or less over the optical wavelength regime, whenmeasured at the anti-reflective surface 122 only (e.g., when removingthe reflections from an uncoated back surface (e.g., 114 in FIG. 1) ofthe article, such as through using index-matching oils on the backsurface coupled to an absorber, or other known methods). The averagereflectance (which may be a photopic average) may be in the range fromabout 0.4% to about 9%, from about 0.4% to about 8%, from about 0.4% toabout 7%, from about 0.4% to about 6%, or from about 0.4% to about 5%and all ranges therebetween. In some instances, the anti-reflectivecoating 120 may exhibit such average light reflectance over otherwavelength ranges such as from about 450 nm to about 650 nm, from about420 nm to about 680 nm, from about 420 nm to about 700 nm, from about420 nm to about 740 nm, from about 420 nm to about 850 nm, or from about420 nm to about 950 nm. In some embodiments, the anti-reflective surface122 exhibits an average light transmission of about 90% or greater, 92%or greater, 94% or greater, 96% or greater, or 98% or greater, over theoptical wavelength regime. Unless otherwise specified, the averagereflectance or transmittance is measured at an incident illuminationangle from about 0 degrees to about 10 degrees (however, suchmeasurements may be provided at incident illumination angles of 45degrees or 60 degrees).

The article 100 may include one or more additional coatings 140 disposedon the anti-reflective coating, as shown in FIG. 6. In one or moreembodiments, the additional coating may include an easy-to-cleancoating. An example of a suitable an easy-to-clean coating is describedin U.S. patent application Ser. No. 13/690,904, entitled “PROCESS FORMAKING OF GLASS ARTICLES WITH OPTICAL AND EASY-TO-CLEAN COATINGS,” filedon Nov. 30, 2012, which is incorporated herein in its entirety byreference. The easy-to-clean coating may have a thickness in the rangefrom about 5 nm to about 50 nm and may include known materials such asfluorinated silanes. The easy-to-clean coating may alternately oradditionally comprise a low-friction coating or surface treatment.Exemplary low-friction coating materials may include diamond-likecarbon, silanes (e.g. fluorosilanes), phosphonates, alkenes, andalkynes. In some embodiments, the easy-to-clean coating may have athickness in the range from about 1 nm to about 40 nm, from about 1 nmto about 30 nm, from about 1 nm to about 25 nm, from about 1 nm to about20 nm, from about 1 nm to about 15 nm, from about 1 nm to about 10 nm,from about 5 nm to about 50 nm, from about 10 nm to about 50 nm, fromabout 15 nm to about 50 nm, from about 7 nm to about 20 nm, from about 7nm to about 15 nm, from about 7 nm to about 12 nm or from about 7 nm toabout 10 nm, and all ranges and sub-ranges therebetween.

The additional coating 140 may include a scratch resistant layer orlayers. In some embodiments, the additional coating 140 includes acombination of easy-to-clean material and scratch resistant material. Inone example, the combination includes an easy-to-clean material anddiamond-like carbon. Such additional coatings 140 may have a thicknessin the range from about 5 nm to about 20 nm. The constituents of theadditional coating 140 may be provided in separate layers. For example,the diamond-like carbon may be disposed as a first layer and the easy-toclean can be disposed as a second layer on the first layer ofdiamond-like carbon. The thicknesses of the first layer and the secondlayer may be in the ranges provided above for the additional coating.For example, the first layer of diamond-like carbon may have a thicknessof about 1 nm to about 20 nm or from about 4 nm to about 15 nm (or morespecifically about 10 nm) and the second layer of easy-to-clean may havea thickness of about 1 nm to about 10 nm (or more specifically about 6nm). The diamond-like coating may include tetrahedral amorphous carbon(Ta—C), Ta—C:H, and/or a-C—H.

As mentioned herein, the optical coating 120 may include a scratchresistant layer 150 or coating (when a plurality of scratch resistantlayers are utilized), which may be disposed between the anti-reflectivecoating 130 and the substrate 110. In some embodiment, the scratchresistant layer 150 or coating is disposed between the layers of theanti-reflective coating 130 (such as 150 as shown in FIG. 7). The twosections of the anti-reflective coating (i.e., a first section disposedbetween the scratch resistant layer 150 and the substrate 110, and asecond section disposed on the scratch resistant layer) may have adifferent thickness from one another or may have essentially the samethickness as one another. The layers of the two sections of theanti-reflective coating may be the same in composition, order, thicknessand/or arrangement as one another or may differ from one another.

Exemplary materials used in the scratch resistant layer 150 or coating(or the scratch-resistant layer/coating used as an additional coating140) may include an inorganic carbide, nitride, oxide, diamond-likematerial, or combination of these. Examples of suitable materials forthe scratch resistant layer or coating include metal oxides, metalnitrides, metal oxynitride, metal carbides, metal oxycarbides, and/orcombinations thereof combination thereof. Exemplary metals include B,Al, Si, Ti, V, Cr, Y, Zr, Nb, Mo, Sn, Hf, Ta and W. Specific examples ofmaterials that may be utilized in the scratch resistant layer or coatingmay include Al₂O₃, AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y),Si_(u)Al_(v)O_(x)N_(y), diamond, diamond-like carbon, Si_(x)C_(y),Si_(x)O_(y)C_(z), ZrO₂, TiO_(x)N_(y) and combinations thereof. Thescratch resistant layer or coating may also comprise nanocompositematerials, or materials with a controlled microstructure to improvehardness, toughness, or abrasion/wear resistance. For example thescratch resistant layer or coating may comprise nanocrystallites in thesize range from about 5 nm to about 30 nm. In embodiments, the scratchresistant layer or coating may comprise transformation-toughenedzirconia, partially stabilized zirconia, or zirconia-toughened alumina.In embodiments, the scratch resistant layer or coating exhibits afracture toughness value greater than about 1 MPa√m and simultaneouslyexhibits a hardness value greater than about 8 GPa.

The scratch resistant layer may include a single layer 150 (as shown inFIG. 7), or multiple sub-layers or sub-layers or single layers thatexhibit a refractive index gradient. Where multiple layers are used,such layers form a scratch resistant coating. For example, a scratchresistant coating may include a compositional gradient ofSi_(u)Al_(v)O_(x)N_(y) where the concentration of any one or more of Si,Al, O and N are varied to increase or decrease the refractive index. Therefractive index gradient may also be formed using porosity. Suchgradients are more fully described in U.S. patent application Ser. No.14/262,224, entitled “Scratch-Resistant Articles with a Gradient Layer”,filed on Apr. 28, 2014, which is hereby incorporated by reference in itsentirety.

In one embodiment, depicted in FIG. 8, the optical coating 120 maycomprise a scratch resistant layer 150 that is integrated as a high RIlayer, and one or more low RI layers 130A and high RI layers 130B may bepositioned over the scratch resistant layer 150, with an optionalcapping layer 131 positioned over the low RI layers 130A and high RIlayers 130B, where the capping layer 131 comprises a low RI material.The scratch resistant layer may be alternately defined as the thickesthard layer or the thickest high RI layer in the overall optical coatingor in the overall article. Without being bound by theory, it is believedthat the article 100 may exhibit increased hardness at indentationdepths when a relatively thin amount of material is deposited over thescratch resistant layer 150. However, the inclusion of low RI and highRI layers over the scratch resistant layer 150 may enhance the opticalproperties of the article 100. In some embodiments, relatively fewlayers (e.g., only 1, 2, 3, 4, or 5 layers) may positioned over thescratch resistant layer 150 and these layers may each be relatively thin(e.g. less than 100 nm, less than 75 nm, less than 50 nm, or even lessthan 25 nm).

In embodiments, the layers deposited over the scratch resistant layer150 (i.e., on the air side of the scratch resistant layer 150) may havea total thickness (i.e., in combination) of less than or equal to about1000 nm, less than or equal to about 500 nm, less than or equal to about450 nm, less than or equal to about 400 nm, less than or equal to about350 nm, less than or equal to about 300 nm, less than or equal to about250 nm, less than or equal to about 225 nm, less than or equal to about200 nm, less than or equal to about 175 nm, less than or equal to about150 nm, less than or equal to about 125 nm, less than or equal to about100 nm, less than or equal to about 90 nm, less than or equal to about80 nm, less than or equal to about 70 nm, less than or equal to about 60nm, or even less than or equal to about 50 nm.

In embodiments, the total thickness of low RI layer(s) (the sum ofthickness of all low RI layers, even if they are not in contact) thatare positioned over the scratch resistant layer 150 (i.e., on the airside of the scratch resistant layer 150) may be less than or equal toabout 500 nm, less than or equal to about 450 nm, less than or equal toabout 400 nm, less than or equal to about 350 nm, less than or equal toabout 300 nm, less than or equal to about 250 nm, less than or equal toabout 225 nm, less than or equal to about 200 nm, less than or equal toabout 175 nm, less than or equal to about 150 nm, less than or equal toabout 125 nm, less than or equal to about 100 nm, less than or equal toabout 90 nm, less than or equal to about 80 nm, less than or equal toabout 70 nm, less than or equal to about 60 nm, less than or equal toabout 50 nm, less than or equal to about 40 nm, less than or equal toabout 30 nm, less than or equal to about 20 nm, or even less than orequal to about 10 nm.

In embodiments, the optical coating 120 may comprise, in the uppermost500 nm of thickness (i.e., on the air side of the optical coating 120),at least about 50%, at least about 55%, at least about 60%, at leastabout 65%, at least about 70%, at least about 75%, at least about 80%,at least about 85%, at least about 90%, or even at least about 95% ofhigh RI (high hardness) material, when calculated as a thicknesspercentage or a volume percentage of the uppermost 500 nm of material.For example, when the layers positioned over the scratch resistant layer150 are relatively thin, the scratch resistant layer 150 which may bemade of a hard material may comprise the majority of the uppermost 500nm of the optical coating 120. In embodiments, the optical coating 120may comprise, in the uppermost 500 nm of thickness (i.e., on the airside of the optical coating 120), less than about 50%, less than about45%, less than about 40%, less than about 35%, less than about 30%, lessthan about 25%, less than about 20%, less than about 15%, less thanabout 10%, or even less than about 5% of low RI (low hardness) material.

The composition of the scratch resistant layer or coating may bemodified to provide specific properties (e.g., hardness). In one or moreembodiments, the scratch resistant layer or coating exhibits a maximumhardness in the range from about 5 GPa to about 30 GPa as measured on amajor surface of the scratch resistant layer or coating, by theBerkovitch Indenter Hardness Test. In one or more embodiments, thescratch resistant layer or coating exhibits a maximum hardness in therange from about 6 GPa to about 30 GPa, from about 7 GPa to about 30GPa, from about 8 GPa to about 30 GPa, from about 9 GPa to about 30 GPa,from about 10 GPa to about 30 GPa, from about 12 GPa to about 30 GPa,from about 5 GPa to about 28 GPa, from about 5 GPa to about 26 GPa, fromabout 5 GPa to about 24 GPa, from about 5 GPa to about 22 GPa, fromabout 5 GPa to about 20 GPa, from about 12 GPa to about 25 GPa, fromabout 15 GPa to about 25 GPa, from about 16 GPa to about 24 GPa, fromabout 18 GPa to about 22 GPa and all ranges and sub-ranges therebetween.In one or more embodiments, the scratch resistant coating may exhibit amaximum hardness that is greater than 15 GPa, greater than 20 GPa, orgreater than 25 GPa. In one or more embodiments, the scratch resistantlayer exhibits a maximum hardness in the range from about 15 GPa toabout 150 GPa, from about 15 GPa to about 100 GPa, or from about 18 GPato about 100 GPa. Maximum hardness is the highest hardness valuemeasured over a range of indentation depths. Such maximum hardnessvalues are exhibited along an indentation depth of about 50 nm orgreater or 100 nm or greater (e.g., from about 100 nm to about 300 nm,from about 100 nm to about 400 nm, from about 100 nm to about 500 nm,from about 100 nm to about 600 nm, from about 200 nm to about 300 nm,from about 200 nm to about 400 nm, from about 200 nm to about 500 nm, orfrom about 200 nm to about 600 nm).

In embodiments, the article 100 comprises a hardness profile, which maybe defined by the nanohardness of the article at a combination ofindentation depths. For example, the article may exhibit a hardnessprofile where the article 100 has a nanohardness of greater than aspecified value at about a 100 nm indentation depth and/or ananohardness of greater than another specified value at about a 300 nmindentation depth and/or a nanohardness of greater than anotherspecified value at about a 500 nm indentation depth and/or ananohardness of greater than another specified value at about a 700 nmindentation depth. For example two or more indentations depths may beselected to establish a hardness profile. Having high hardness thatextends out to deeper indentation depths helps protect against moresevere scratch events responsible for more visible scratches.Maintaining higher hardness at shallower indentation depths helps toprotect against less severe scratch events. Accordingly, it is desirableto have a hardness profile wherein the hardness quickly increases atshallow indentation depths (for example, from the surface up to 100 nm),and is maintained as deep as possible, for example at depths from 100 nmup to about 700 or 800 nm, as measured from the surface. In embodiments,the article 100 may comprise a hardness of at least about 5 GPa, atleast about 6 GPa, at least about at least about 7 GPa, at least about 8GPa, at least about 9 GPa, at least about 10 GPa, at least about 11 GPa,at least about 12 GPa, at least about 13 GPa, at least about 14 GPa, atleast about 15 GPa, at least about 16 GPa, at least about 17 GPa, atleast about 18 GPa, at least about 19 GPa, at least about 20 GPa, atleast about 22 GPa, or even at least about 25 GPa at an indentationdepth of 100 nm; may also comprise a harness of at least about 5 GPa, atleast about 6 GPa, at least about at least about 7 GPa, at least about 8GPa, at least about 9 GPa, at least about 10 GPa, at least about 11 GPa,at least about 12 GPa, at least about 13 GPa, at least about 14 GPa, atleast about 15 GPa, at least about 16 GPa, at least about 17 GPa, atleast about 18 GPa, at least about 19 GPa, at least about 20 GPa, atleast about 22 GPa, or even at least about 25 GPa at an indentationdepth of 300 nm; may comprise a hardness of at least about 5 GPa, atleast about 6 GPa, at least about at least about 7 GPa, at least about 8GPa, at least about 9 GPa, at least about 10 GPa, at least about 11 GPa,at least about 12 GPa, at least about 13 GPa, at least about 14 GPa, atleast about 15 GPa, at least about 16 GPa, at least about 17 GPa, atleast about 18 GPa, at least about 19 GPa, at least about 20 GPa, atleast about 22 GPa, or even at least about 25 GPa at an indentationdepth of 500 nm; and/or may comprise a hardness of at least about 5 GPa,at least about 6 GPa, at least about at least about 7 GPa, at leastabout 8 GPa, at least about 9 GPa, at least about 10 GPa, at least about11 GPa, at least about 12 GPa, at least about 13 GPa, at least about 14GPa, at least about 15 GPa, at least about 16 GPa, at least about 17GPa, at least about 18 GPa, at least about 19 GPa, at least about 20GPa, at least about 22 GPa, or even at least about 25 GPa at anindentation depth of 700 nm. For example, embodiments described hereinmay have a hardness of at least about 12 GPa at a 100 nm indentationdepth, a hardness of at least about 15 GPa at a 300 nm indentationdepth, a hardness of at least about 15 GPa at a 500 nm indentationdepth, and a hardness of at least about 15 GPa at a 700 nm indentationdepth.

The physical thickness of the scratch resistant coating or layer may bein the range from about 1 nm to about 5 μm. In some embodiments, thephysical thickness of the scratch resistant coating may be in the rangefrom about 1 nm to about 3 μm, from about 1 nm to about 2.5 μm, fromabout 1 nm to about 2 μm, from about 1 nm to about 1.5 μm, from about 1nm to about 1 μm, from about 1 nm to about 0.5 μm, from about 1 nm toabout 0.2 μm, from about 1 nm to about 0.1 μm, from about 1 nm to about0.05 μm, from about 5 nm to about 0.05 μm, from about 10 nm to about0.05 μm, from about 15 nm to about 0.05 μm, from about 20 nm to about0.05 μm, from about 5 nm to about 0.05 μm, from about 200nm to about 3μm, from about 400 nm to about 3 μm, from about 800 nm to about 3 μm,and all ranges and sub-ranges therebetween. In some embodiments, thephysical thickness of the scratch resistant coating may be in the rangefrom about 1 nm to about 25 nm. In some instances, the scratch-resistantlayer may include a nitride or an oxy-nitride material and may have athickness of about 200 nm or greater, 500 nm or greater or about 1000 nmor greater.

The article of one or more embodiments may be described as abrasionresistant as measured by various methods, after being abraded on theanti-reflective surface 122 according to a Taber Test after at leastabout 500 cycles. Various forms of abrasion test are known in the art,such as the test method specified in ASTM D1044-99, using abrasive mediasupplied by Taber Industries. Modified abrasion methods related to ASTMD1044-99 can be created using different types of abrading media,abradant geometry and motion, pressure, etc. in order to providerepeatable and measurable abrasion or wear tracks to meaningfullydifferentiate the abrasion resistance of different samples. For example,different test conditions will usually be appropriate for soft plasticsvs. hard inorganic test samples. The embodiments described herein weresubjected to a Taber Test, as defined herein, which is a specificmodified version of ASTM D1044-99 that gives clear and repeatabledifferentiation of durability between different samples which compriseprimarily hard inorganic materials, such as oxide glasses and oxide ornitride coatings. As used herein, the phrase “Taber Test” refers to atest method using a Taber Linear Abraser 5750 (TLA 5750) and accessoriessupplied by Taber Industries, in an environment including a temperatureof about 22° C.±3° C. and Relative Humidity of up to about 70%. The TLA5750 includes a CS-17 abraser material having a 6.7 mm diameter abraserhead. Each sample was abraded according to the Taber Test and theabrasive damage was evaluated using both Haze and BidirectionalTransmittance Distribution Function (CCBTDF) measurements, among othermethods. In the Taber Test, the procedure for abrading each sampleincludes placing the TLA 5750 and a flat sample support on a rigid, flatsurface and securing the TLA 5750 and the sample support to the surface.Before each sample is abraded under the Taber Test, the abraser isrefaced using a new S-14 refacing strip adhered to glass. The abraser issubjected to 10 refacing cycles using a cycle speed of 25 cycles/minuteand stroke length of 1 inch, with no additional weight added (i.e., atotal weight of about 350 g is used during refacing, which is thecombined weight of the spindle and collet holding the abraser). Theprocedure then includes operating the TLA 5750 to abrade the sample,where the sample is placed in the sample support in contact with theabraser head and supporting the weight applied to the abraser head,using a cycle speed of 25 cycles/minute, and a stroke length of 1 inch,and a weight such that the total weight applied to the sample is 850 g(i.e., a 500 g auxiliary weight is applied in addition to the 350 gcombined weight of the spindle and collet). The procedure includesforming two wear tracks on each sample for repeatability, and abradingeach sample for 500 cycle counts in each of the two wear tracks on eachsample.

In one or more embodiments, the anti-reflective surface 122 of thearticle 100 is abraded according to the above Taber Test and the articleexhibits a haze of about 10% of less, as measured on the abraded sideusing a hazemeter supplied by BYK Gardner under the trademark Haze-Gardplus®, using an aperture over the source port, the aperture having adiameter of 8 mm.

The article 100 of one or more embodiments exhibits such abrasionresistance with and without any additional coatings (including theadditional coating 140, which will be described herein). In someembodiments, the haze may be about 9% or less, about 8% or less, about7% or less, about 6% or less, about 5% or less, about 4% or less, about3% or less, about 2% or less, about 1% or less, about 0.5% or less orabout 0.3% or less. In some specific embodiments, the article 100exhibits a haze in the range from about 0.1% to about 10%, from about0.1% to about 9%, from about 0.1% to about 8%, from about 0.1% to about7%, from about 0.1% to about 6%, from about 0.1% to about 5%, from about0.1% to about 4%, from about 0.1% to about 3%, from about 0.1% to about2%, from about 0.1% to about 1%, 0.3% to about 10%, from about 0.5% toabout 10%, from about 1% to about 10%, from about 2% to about 10%, fromabout 3% to about 10%, from about 4% to about 10%, from about 5% toabout 10%, from about 6% to about 10%, from about 7% to about 10%, fromabout 1% to about 8%, from about 2% to about 6%, from about 3% to about5%, and all ranges and sub-ranges therebetween.

Alternate methods for quantifying the abrasion resistance are alsocontemplated here. In one or more embodiments, article 100 abraded bythe Taber Test on the anti-reflective surface 122 may exhibit anabrasion resistance as measured by atomic force microscopy (AFM) surfaceprofiling, which may be carried out for example over an 80×80 micronarea, or multiple 80×80 micron areas (to sample a larger portion of theabraded area) of the anti-reflective surface 122. From these AFM surfacescans, surface roughness statistics such as RMS roughness, Ra roughness,and peak-to-valley surface height may be evaluated. In one or moreembodiments, the article 100 (or specifically, the anti-reflectivesurface 122) may exhibit average surface roughness (Ra) values of about50 nm or less, about 25 nm or less, about 12 nm or less, about 10 nm orless, or about 5 nm or less, after being abraded under the Taber Testdescribed above.

In one or more embodiments, the article 100 may exhibit an abrasionresistance, after the anti-reflective surface 122 is abraded by theTaber Test as measured by a light scattering measurement. In one or moreembodiments, the light scattering measurement includes a bi-directionalreflectance distribution function (BRDF) or bi-directional transmittancedistribution function (BTDF) measurement carried out using a RadiantZemax IS-SA™ instrument. This instrument has the flexibility to measurelight scattering using any input angle from normal to about 85 degreesincidence in reflection, and from normal to about 85 degrees incidencein transmission, while also capturing all scattered light output ineither reflection or transmission into 2*Pi steradians (a fullhemisphere in reflection or transmission). In one embodiment, thearticle 100 exhibits an abrasion resistance, as measured using BTDF atnormal incidence and analyzing the transmitted scattered light at aselected angular range, for example from about 10° to about 80° degreesin polar angles and any angular range therein. The full azimuthal rangeof angles can be analyzed and integrated, or particular azimuthalangular slices can be selected, for example from about 0° and 90°azimuthally. In the case of linear abrasion, it may be desired to choosean azimuthal direction that is substantially orthogonal to the abrasiondirection so as to increase signal-to-noise of the optical scatteringmeasurement. In one or more embodiments, the article 100 may exhibit ascattered light intensity as measured at the anti-reflective coating120, of about less than about 0.1, about 0.05 or less, about 0.03 orless, about 0.02 or less, about 0.01 or less, about 0.005 or less, orabout 0.003 or less (in units of 1/steradian), when using the RadiantZemax IS-SA tool in CCBTDF mode at normal incidence in transmission,with a 2 mm aperture and a monochrometer set to 600 nm wavelength, andwhen evaluated at polar scattering angles in the range from about 15° toabout 60° (e.g. specifically, about 20° or about 40°). Normal incidencein transmission may be otherwise known as zero degrees in transmission,which may be denoted as 180° incidence by the instrument software. Inone or more embodiments, the scattered light intensity may be measuredalong an azimuthal direction substantially orthogonal to the abradeddirection of a sample abraded by the Taber Test. In one example, theTaber Test may use from about 10 cycles to about 1000 cycles, and allvalues in between. These optical intensity values may also correspond toless than about 1%, less than about 0.5%, less than about 0.2%, or lessthan about 0.1% of the input light intensity that is scattered intopolar scattering angles greater than about 5 degrees, greater than about10 degrees, greater than about 30 degrees, or greater than about 45degrees.

Generally speaking, BTDF testing at normal incidence, as describedherein, is closely related to the transmission haze measurement, in thatboth are measuring the amount of light that is scattered in transmissionthrough a sample (or, in this case the article 100, after abrading theanti-reflective coating 120). BTDF measurements provide more sensitivityas well as more detailed angular information, compared to hazemeasurements. BTDF allows measurement of scattering into different polarand azimuthal angles, for example allowing us to selectively evaluatethe scattering into azimuthal angles that are substantially orthogonalto the abrasion direction in the linear Taber test (these are the angleswhere light scattering from linear abrasion is the highest).Transmission haze is essentially the integration of all scattered lightmeasured by normal incidence BTDF into the entire hemisphere of polarangles greater than about +/−2.5 degrees.

The optical coating 120 and the article 100 may be described in terms ofa hardness measured by a Berkovich Indenter Hardness Test. As usedherein, the “Berkovich Indenter Hardness Test” includes measuring thehardness of a material on a surface thereof by indenting the surfacewith a diamond Berkovich indenter. The Berkovich Indenter Hardness Testincludes indenting the anti-reflective surface 122 of the article or thesurface of the optical coating 120 (or the surface of any one or more ofthe layers in the anti-reflective coating) with the diamond Berkovichindenter to form an indent to an indentation depth in the range fromabout 50 nm to about 1000 nm (or the entire thickness of theanti-reflective coating or layer, whichever is less) and measuring themaximum hardness from this indentation along the entire indentationdepth range or a segment of this indentation depth (e.g., in the rangefrom about 100 nm to about 600 nm), generally using the methods setforth in Oliver, W. C.; Pharr, G. M. An improved technique fordetermining hardness and elastic modulus using load and displacementsensing indentation experiments. J. Mater. Res., Vol. 7, No. 6, 1992,1564-1583; and Oliver, W. C.; Pharr, G. M. Measurement of Hardness andElastic Modulus by Instrument Indentation: Advances in Understanding andRefinements to Methodology. J. Mater. Res., Vol. 19, No. 1, 2004, 3-20.As used herein, hardness refers to a maximum hardness, and not anaverage hardness.

Typically, in nanoindentation measurement methods (such as by using aBerkovich indenter) of a coating that is harder than the underlyingsubstrate, the measured hardness may appear to increase initially due todevelopment of the plastic zone at shallow indentation depths and thenincreases and reaches a maximum value or plateau at deeper indentationdepths. Thereafter, hardness begins to decrease at even deeperindentation depths due to the effect of the underlying substrate. Wherea substrate having an increased hardness compared to the coating isutilized, the same effect can be seen; however, the hardness increasesat deeper indentation depths due to the effect of the underlyingsubstrate.

The indentation depth range and the hardness values at certainindentation depth range(s) can be selected to identify a particularhardness response of the optical film structures and layers thereof,described herein, without the effect of the underlying substrate. Whenmeasuring hardness of the optical film structure (when disposed on asubstrate) with a Berkovich indenter, the region of permanentdeformation (plastic zone) of a material is associated with the hardnessof the material. During indentation, an elastic stress field extendswell beyond this region of permanent deformation. As indentation depthincreases, the apparent hardness and modulus are influenced by stressfield interactions with the underlying substrate. The substrateinfluence on hardness occurs at deeper indentation depths (i.e.,typically at depths greater than about 10% of the optical film structureor layer thickness). Moreover, a further complication is that thehardness response requires a certain minimum load to develop fullplasticity during the indentation process. Prior to that certain minimumload, the hardness shows a generally increasing trend.

At small indentation depths (which also may be characterized as smallloads) (e.g., up to about 50 nm), the apparent hardness of a materialappears to increase dramatically versus indentation depth. This smallindentation depth regime does not represent a true metric of hardnessbut instead, reflects the development of the aforementioned plasticzone, which is related to the finite radius of curvature of theindenter. At intermediate indentation depths, the apparent hardnessapproaches maximum levels. At deeper indentation depths, the influenceof the substrate becomes more pronounced as the indentation depthsincrease. Hardness may begin to drop dramatically once the indentationdepth exceeds about 30% of the optical film structure thickness or thelayer thickness.

FIG. 9 illustrates the changes in measured hardness value as a functionof indentation depth and thickness of a coating. As shown in FIG. 9, thehardness measured at intermediate indentation depths (at which hardnessapproaches and is maintained at maximum levels) and at deeperindentation depths depends on the thickness of a material or layer. FIG.9 illustrates the hardness response of four different layers ofAlO_(x)N_(y) having different thicknesses. The hardness of each layerwas measured using the Berkovich Indenter Hardness Test. The 500nm-thick layer exhibited its maximum hardness at indentation depths fromabout 100 nm to 180 nm, followed by a dramatic decrease in hardness atindentation depths from about 180 nm to about 200 nm, indicating thehardness of the substrate influencing the hardness measurement. The 1000nm-thick layer exhibited a maximum hardness at indentation depths fromabout 100 nm to about 300 nm, followed by a dramatic decrease inhardness at indentation depths greater than about 300 nm. The 1500nm-thick layer exhibited a maximum hardness at indentation depths fromabout 100 nm to about 550 nm and the 2000-nm thick layer exhibited amaximum hardness at indentation depths from about 100 nm to about 600nm. Although FIG. 9 illustrates a thick single layer, the same behavioris observed in thinner coatings and those including multiple layers suchas the anti-reflective coating 120 of the embodiments described herein.

In some embodiments, the optical 120 may exhibit a hardness of about 8GPa or greater, about 10 GPa or greater or about 12 GPa or greater(e.g., 14 GPa or greater, 16 GPa or greater, 18 GPa or greater, 20 GPaor greater). The hardness of the optical coating 120 may be up to about20 GPa or 30 GPa. The article 100, including the anti-reflective coating120 and any additional coatings, as described herein, exhibit a hardnessof about 5 GPa or greater, about 8 GPa or greater, about 10 GPa orgreater or about 12 GPa or greater (e.g., 14 GPa or greater, 16 GPa orgreater, 18 GPa or greater, 20 GPa or greater), as measured on theanti-reflective surface 122, by a Berkovitch Indenter Hardness Test. Thehardness of the optical 120 may be up to about 20 GPa or 30 GPa. Suchmeasured hardness values may be exhibited by the optical coating 120and/or the article 100 along an indentation depth of about 50 nm orgreater or about 100 nm or greater (e.g., from about 100 nm to about 300nm, from about 100 nm to about 400 nm, from about 100 nm to about 500nm, from about 100 nm to about 600 nm, from about 200 nm to about 300nm, from about 200 nm to about 400 nm, from about 200 nm to about 500nm, or from about 200 nm to about 600 nm). In one or more embodiments,the article exhibits a hardness that is greater than the hardness of thesubstrate (which can be measured on the opposite surface from theanti-reflective surface).

The optical coating 120 may have at least one layer having a hardness(as measured on the surface of such layer, e.g., surface of the secondhigh RI layer 130B of FIG. 2 or the surface of the scratch resistantlayer) of about 12 GPa or greater, about 13 GPa or greater, about 14 GPaor greater, about 15 GPa or greater, about 16 GPa or greater, about 17GPa or greater, about 18 GPa or greater, about 19 GPa or greater, about20 GPa or greater, about 22 GPa or greater, about 23 GPa or greater,about 24 GPa or greater, about 25 GPa or greater, about 26 GPa orgreater, or about 27 GPa or greater (up to about 50 GPa), as measured bythe Berkovich Indenter Hardness Test. The hardness of such layer may bein the range from about 18 GPa to about 21 GPa, as measured by theBerkovich Indenter Hardness Test. Such measured hardness values may beexhibited by the at least one layer along an indentation depth of about50 nm or greater or 100 nm or greater (e.g., from about 100 nm to about300 nm, from about 100 nm to about 400 nm, from about 100 nm to about500 nm, from about 100 nm to about 600 nm, from about 200 nm to about300 nm, from about 200 nm to about 400 nm, from about 200 nm to about500 nm, or from about 200 nm to about 600 nm).

In one or more embodiments, the optical coating 120 or individual layerswithin the optical coating may exhibit an elastic modulus of about 75GPa or greater, about 80 GPa or greater or about 85 GPa or greater, asmeasured on the anti-reflective surface 122, by indenting that surfacewith a Berkovitch indenter. These modulus values may represent a modulusmeasured very close to the anti-reflective surface, e.g. at indentationdepths of 0 nm to about 50 nm, or it may represent a modulus measured atdeeper indentation depths, e.g. from about 50 nm to about 1000 nm.

In embodiments of the article which include a scratch-resistant layer(when used as part of the anti-reflective coating, e.g., 150 of FIG. 7)or scratch resistant coating (when used as an additional coating 140),the article may exhibit a maximum hardness in the range from about 12GPa to about 25 GPa, as measured by the Berkovich Indenter Hardness Teston the anti-reflective surface 122, or the surface of the scratchresistant coating, respectively. Such measured hardness values may beexhibited along an indentation depth of about 50 nm or greater or 100 nmor greater (e.g., from about 100 nm to about 300 nm, from about 100 nmto about 400 nm, from about 100 nm to about 500 nm, from about 100 nm toabout 600 nm, from about 200 nm to about 300 nm, from about 200 nm toabout 400 nm, from about 200 nm to about 500 nm, or from about 200 nm toabout 600 nm). This hardness may be exhibited even when the scratchresistant layer is not disposed at or near the anti-reflective surface122 (e.g., as shown in FIGS. 7 and 8).

Optical interference between reflected waves from the optical coating120/air interface and the optical coating 120/substrate 110 interfacecan lead to spectral reflectance and/or transmittance oscillations thatcreate apparent color in the article 100. As used herein, the term“transmittance” is defined as the percentage of incident optical powerwithin a given wavelength range transmitted through a material (e.g.,the article, the substrate or the optical film or portions thereof). Theterm “reflectance” is similarly defined as the percentage of incidentoptical power within a given wavelength range that is reflected from amaterial (e.g., the article, the substrate, or the optical film orportions thereof). Transmittance and reflectance are measured using aspecific linewidth. In one or more embodiments, the spectral resolutionof the characterization of the transmittance and reflectance is lessthan 5 nm or 0.02 eV. The color may be more pronounced in reflection.The angular color shifts in reflection with viewing angle due to a shiftin the spectral reflectance oscillations with incident illuminationangle. Angular color shifts in transmittance with viewing angle are alsodue to the same shift in the spectral transmittance oscillation withincident illumination angle. The observed color and angular color shiftswith incident illumination angle are often distracting or objectionableto device users, particularly under illumination with sharp spectralfeatures such as fluorescent lighting and some LED lighting. Angularcolor shifts in transmission may also play a factor in color shift inreflection and vice versa. Factors in angular color shifts intransmission and/or reflection may also include angular color shifts dueto viewing angle or angular color shifts away from a certain white pointthat may be caused by material absorption (somewhat independent ofangle) defined by a particular illuminant or test system.

The oscillations may be described in terms of amplitude. As used herein,the term “amplitude” includes the peak-to-valley change in reflectanceor transmittance. The phrase “average amplitude” includes thepeak-to-valley change in reflectance or transmittance averaged overseveral oscillation cycles or wavelength sub-ranges within the opticalwavelength regime. As used herein, the “optical wavelength regime”includes the wavelength range from about 400 nm to about 800 nm (andmore specifically from about 450 nm to about 650 nm).

The embodiments of this disclosure include an anti-reflective coating toprovide improved optical performance, in terms of colorlessness and/orsmaller angular color shifts with viewed at varying incidentillumination angles from normal incidence under different illuminants.

One aspect of this disclosure pertains to an article that exhibitscolorlessness in reflectance and/or transmittance even when viewed atdifferent incident illumination angles under an illuminant. In one ormore embodiments, the article exhibits an angular color shift inreflectance and/or transmittance of about 5 or less or about 2 or lessbetween a reference illumination angle and any incidental illuminationangles in the ranges provided herein. As used herein, the phrase “colorshift” (angular or reference point) refers to the change in both a* andb*, under the CIE L*, a*, b* colorimetry system in reflectance and/ortransmittance. It should be understood that unless otherwise noted, theL* coordinate of the articles described herein are the same at any angleor reference point and do not influence color shift. For example,angular color shift may be determined using the following Equation (1):

√((a*₂−a*₁)²+(b*₂−b*₁)²),   (1)

with a*₁, and b*₁ representing the a* and b* coordinates of the articlewhen viewed at incidence reference illumination angle (which may includenormal incidence) and a*₂, and b*₂ representing the a* and b*coordinates of the article when viewed at an incident illuminationangle, provided that the incident illumination angle is different fromthe reference illumination angle and in some cases differs from thereference illumination angle by at least about 1 degree, 2 degrees orabout 5 degrees. In some instances, an angular color shift inreflectance and/or transmittance of about 10 or less (e.g., 5 or less, 4or less, 3 or less, or 2 or less) is exhibited by the article whenviewed at various incident illumination angles from a referenceillumination angle, under an illuminant. In some instances the angularcolor shift in reflectance and/or transmittance is about 1.9 or less,1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 orless, 1.2 or less, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 orless, or 0.1 or less. In some embodiments, the angular color shift maybe about 0. The illuminant can include standard illuminants asdetermined by the CIE, including A illuminants (representingtungsten-filament lighting), B illuminants (daylight simulatingilluminants), C illuminants (daylight simulating illuminants), D seriesilluminants (representing natural daylight), and F series illuminants(representing various types of fluorescent lighting). In specificexamples, the articles exhibit an angular color shift in reflectanceand/or transmittance of about 2 or less when viewed at incidentillumination angle from the reference illumination angle under a CIE F2,F10, F11, F12 or D65 illuminant, or more specifically, under a CIE F2illuminant.

The reference illumination angle may include normal incidence (i.e.,from about 0 degrees to about 10 degrees), or 5 degrees from normalincidence, 10 degrees from normal incidence, 15 degrees from normalincidence, 20 degrees from normal incidence, 25 degrees from normalincidence, 30 degrees from normal incidence, 35 degrees from normalincidence, 40 degrees from normal incidence, 50 degrees from normalincidence, 55 degrees from normal incidence, or 60 degrees from normalincidence, provided the difference between the reference illuminationangle and the difference between the incident illumination angle and thereference illumination angle is at least about 1 degree, 2 degrees orabout 5 degrees. The incident illumination angle may be, with respect tothe reference illumination angle, in the range from about 5 degrees toabout 80 degrees, from about 5 degrees to about 70 degrees, from about 5degrees to about 65 degrees, from about 5 degrees to about 60 degrees,from about 5 degrees to about 55 degrees, from about 5 degrees to about50 degrees, from about 5 degrees to about 45 degrees, from about 5degrees to about 40 degrees, from about 5 degrees to about 35 degrees,from about 5 degrees to about 30 degrees, from about 5 degrees to about25 degrees, from about 5 degrees to about 20 degrees, from about 5degrees to about 15 degrees, and all ranges and sub-ranges therebetween,away from the reference illumination angle. The article may exhibit theangular color shifts in reflectance and/or transmittance describedherein at and along all the incident illumination angles in the rangefrom about 2 degrees to about 80 degrees (or from about 10 degrees toabout 80 degrees, or from about 20 degrees to about 80 degrees), whenthe reference illumination angle is normal incidence. In someembodiments, the article may exhibit the angular color shifts inreflectance and/or transmittance described herein at and along all theincident illumination angles in the range from about 2 degrees to about80 degrees (or from about 10 degrees to about 80 degrees, or from about20 degrees to about 80 degrees), when the difference between theincident illumination angle and the reference illumination angle is atleast about 1 degree, 2 degrees or about 5 degrees. In one example, thearticle may exhibit an angular color shift in reflectance and/ortransmittance of 5 or less (e.g., 4 or less, 3 or less or about 2 orless) at any incident illumination angle in the range from about 2degrees to about 60 degrees, from about 5 degrees to about 60 degrees,or from about 10 degrees to about 60 degrees away from a referenceillumination angle equal to normal incidence. In other examples, thearticle may exhibit an angular color shift in reflectance and/ortransmittance of 5 or less (e.g., 4 or less, 3 or less or about 2 orless) when the reference illumination angle is 10 degrees and theincident illumination angle is any angle in the range from about 12degrees to about 60 degrees, from about 15 degrees to about 60 degrees,or from about 20 degrees to about 60 degrees away from the referenceillumination angle.

In some embodiments, the angular color shift may be measured at allangles between a reference illumination angle (e.g., normal incidence)and an incident illumination angle in the range from about 20 degrees toabout 80 degrees. In other words, the angular color shift may bemeasured and may be less than about 5 or less than about 2, at allangles in the range from about 0 degrees and 20 degrees, from about 0degrees to about 30 degrees, from about 0 degrees to about 40 degrees,from about 0 degrees to about 50 degrees, from about 0 degrees to about60 degrees or from about 0 degrees to about 80 degrees.

In one or more embodiments, the article exhibits a color in the CIE L*,a*, b* colorimetry system in reflectance and/or transmittance such thatthe distance or reference point color shift between the transmittancecolor or reflectance coordinates from a reference point is less thanabout 5 or less than about 2 under an illuminant (which can includestandard illuminants as determined by the CIE, including A illuminants(representing tungsten-filament lighting), B illuminants (daylightsimulating illuminants), C illuminants (daylight simulatingilluminants), D series illuminants (representing natural daylight), andF series illuminants (representing various types of fluorescentlighting)). In specific examples, the articles exhibit a color shift inreflectance and/or transmittance of about 2 or less when viewed atincident illumination angle from the reference illumination angle undera CIE F2, F10, F11, F12 or D65 illuminant or more specifically under aCIE F2 illuminant. Stated another way, the article may exhibit atransmittance color (or transmittance color coordinates) and/or areflectance color (or reflectance color coordinates) measured at theanti-reflective surface 122 having a reference point color shift of lessthan about 2 from a reference point, as defined herein. Unless otherwisenoted, the transmittance color or transmittance color coordinates aremeasured on two surfaces of the article including at the anti-reflectivesurface 122 and the opposite bare surface of the article (i.e., 114).Unless otherwise noted, the reflectance color or reflectance colorcoordinates are measured on only the anti-reflective surface 122 of thearticle. However, the reflectance color or reflectance color coordinatesdescribed herein can be measured on both the anti-reflective surface 122of the article and the opposite side of the article (i.e., major surface114 in FIG. 1) using either a 2-surface measurement (reflections fromtwo sides of an article are both included) or a 1-surface measurement(reflection only from the anti-reflective surface 122 of the article ismeasured). Of these, the 1-surface reflectance measurement is typicallythe more challenging metric to achieve low color or low-color shiftvalues for anti-reflective coatings, and this has relevance toapplications (such as smartphones, etc.) where the back surface of thearticle is bonded to a light absorbing medium such as black ink or anLCD or OLED device).

In one or more embodiments, the reference point may be the origin (0, 0)in the CIE L*, a*, b* colorimetry system (or the color coordinates a*=0,b*=0), the coordinates (a*=−2,b*=−2), or the transmittance orreflectance color coordinates of the substrate. It should be understoodthat unless otherwise noted, the L* coordinate of the articles describedherein are the same as the reference point and do not influence colorshift. Where the reference point color shift of the article is definedwith respect to the substrate, the transmittance color coordinates ofthe article are compared to the transmittance color coordinates of thesubstrate and the reflectance color coordinates of the article arecompared to the reflectance color coordinates of the substrate.

In one or more specific embodiments, the reference point color shift ofthe transmittance color and/or the reflectance color may be less than 1or even less than 0.5. In one or more specific embodiments, thereference point color shift for the transmittance color and/or thereflectance color may be 1.8, 1.6, 1.4, 1.2, 0.8, 0.6, 0.4, 0.2, 0 andall ranges and sub-ranges therebetween. Where the reference point is thecolor coordinates a*=0, b*=0, the reference point color shift iscalculated by Equation (2).

reference point color shift=√((a* _(article))²+(b* _(article))²)   (2)

Where the reference point is the color coordinates a*=−2, b*=−2, thereference point color shift is calculated by Equation (3).

reference point color shift=√((a* _(article)+2)²+(b* _(article)+2)²)  (3)

Where the reference point is the color coordinates of the substrate, thereference point color shift is calculated by Equation (4).

reference point color shift=√((a* _(article) −a* _(substrate))²+(b*_(article) −b* _(substrate))²)   (4)

In some embodiments, the article may exhibit a transmittance color (ortransmittance color coordinates) and a reflectance color (or reflectancecolor coordinates) such that the reference point color shift is lessthan 2 when the reference point is any one of the color coordinates ofthe substrate, the color coordinates a*=0, b*=0 and the coordinatesa*=−2, b*=−2.

In one or more embodiment, the article may exhibit a b* value inreflectance (as measured at the anti-reflective surface only) in therange from about −5 to about 1, from about −5 to about 0, from about −4to about 1, or from about −4 to about 0, in the CIE L*, a*, b*colorimetry system at all incidence illumination angles in the rangefrom about 0 to about 60 degrees (or from about 0 degrees to about 40degrees or from about 0 degrees to about 30 degrees).

In one or more embodiment, the article may exhibit a b* value intransmittance (as measured at the anti-reflective surface and theopposite bare surface of the article) of less than about 2 (or about 1.8or less, about 1.6 or less, 1.5 or less, 1.4 or less, 1.2 or less, orabout 1 or less) in the CIE L*, a*, b* colorimetry system at allincidence illumination angles in the range from about 0 to about 60degrees (or from about 0 degrees to about 40 degrees or from about 0degrees to about 30 degrees). The lower limit of the b* value intransmittance may be about −5.

In some embodiments, the article exhibits an a* value in transmittance(at the anti-reflective surface and the opposite bare surface) in therange from about −1.5 to about 1.5 (e.g., −1.5 to −1.2, −1.5 to −1, −1.2to 1.2, −1 to 1, −1 to 0.5, or −1 to 0) at incident illumination anglesin the range from about 0 degrees to about 60 degrees under illuminantsD65, A, and F2. In some embodiments, the article exhibits a b* value intransmittance (at the anti-reflective surface and the opposite baresurface) in the range from about −1.5 to about 1.5 (e.g., −1.5 to −1.2,−1.5 to −1, −1.2 to 1.2, −1 to 1, −1 to 0.5, or −1 to 0) at incidentillumination angles in the range from about 0 degrees to about 60degrees under illuminants D65, A, and F2.

In some embodiments, the article exhibits an a* value in reflectance (atonly the anti-reflective surface) in the range from about −5 to about 2(e.g., −4.5 to 1.5, −3 to 0, −2.5 to 0.25) at incident illuminationangles in the range from about 0 degrees to about 60 degrees underilluminants D65, A, and F2. In some embodiments, the article exhibits ab* value in reflectance (at only the anti-reflective surface) in therange from about −7 to about 0 at incident illumination angles in therange from about 0 degrees to about 60 degrees under illuminants D65, A,and F2.

The article of one or more embodiments, or the anti-reflective surface122 of one or more articles, may exhibit an average light transmittanceof about 95% or greater (e.g., about 9.5% or greater, about 96% orgreater, about 96.5% or greater, about 97% or greater, about 97.5% orgreater, about 98% or greater, about 98.5% or greater or about 99% orgreater) over the optical wavelength regime in the range from about 400nm to about 800 nm. In some embodiments, the article, or theanti-reflective surface 122 of one or more articles, may exhibit anaverage light reflectance of about 2% or less (e.g., about 1.5% or less,about 1% or less, about 0.75% or less, about 0.5% or less, or about0.25% or less) over the optical wavelength regime in the range fromabout 400 nm to about 800 nm. These light transmittance and lightreflectance values may be observed over the entire optical wavelengthregime or over selected ranges of the optical wavelength regime (e.g., a100 nm wavelength range, 150 nm wavelength range, a 200 nm wavelengthrange, a 250 nm wavelength range, a 280 nm wavelength range, or a 300 nmwavelength range, within the optical wavelength regime). In someembodiments, these light reflectance and transmittance values may be atotal reflectance or total transmittance (taking into accountreflectance or transmittance on both the anti-reflective surface 122 andthe opposite major surface 114) or may be observed on a single side ofthe article, as measured on the anti-reflective surface 122 only(without taking into account the opposite surface). Unless otherwisespecified, the average reflectance or transmittance is measured at anincident illumination angle in the range from about 0 degrees to about10 degrees (however, such measurements may be provided at incidentillumination angles of 45 degrees or 60 degrees).

In some embodiments, the article of one or more embodiments, or theanti-reflective surface 122 of one or more articles, may exhibit anaverage visible photopic reflectance of about 1% or less, about 0.7% orless, about 0.5% or less, or about 0.45% or less over the opticalwavelength regime. These photopic reflectance values may be exhibited atincident illumination angles in the range from about 0° to about 20°,from about 0° to about 40° or from about 0° to about 60°. As usedherein, photopic reflectance mimics the response of the human eye byweighting the reflectance versus wavelength spectrum according to thehuman eye's sensitivity. Photopic reflectance may also be defined as theluminance, or tristimulus Y value of reflected light, according to knownconventions such as CIE color space conventions. The average photopicreflectance is defined in Equation (4) as the spectral reflectance, R(λ)multiplied by the illuminant spectrum, I(λ) and the CIE's color matchingfunction y(λ), related to the eye's spectral response:

$\begin{matrix}{{\langle R_{p}\rangle} = {\int_{380\mspace{14mu} m\; m}^{720\mspace{14mu} n\; m}{{R(\lambda)} \times {I(\lambda)} \times {\overset{\_}{y}(\lambda)}d\; \lambda}}} & (5)\end{matrix}$

In some embodiments, the article exhibits a single-side average photopicreflectance, measured at normal or near-normal incidence (e.g. 0-10degrees) on the anti-reflective surface only of less than about 10%. Insome embodiments, the single-side average photopic reflectance is about9% or less, about 8% or less, about 7% or less, about 6% or less, about5% or less, about 4% or less, about 3%, or about 2% or less. In aspecific embodiment, the anti-reflective surface 122 of one or morearticles (i.e. when measuring the anti-reflective surface only through asingle-sided measurement), may exhibit the above average photopicreflectance values, while simultaneously exhibiting a maximumreflectance color shift, over the entire incident illumination anglerange from about 5 degrees to about 60 degrees (with the referenceillumination angle being normal incidence) using D65 illumination and/orF2 illuminant, of less than about 5.0, less than about 4.0, less thanabout 3.0, less than about 2.0, less than about 1.5, or less than about1.25. These maximum reflectance color shift values represent the lowestcolor point value measured at any angle from about 5 degrees to about 60degrees from normal incidence, subtracted from the highest color pointvalue measured at any angle in the same range. The values may representa maximum change in a* value (a*_(highest)−a*_(lowest)), a maximumchange in b* value (b*_(highest)−b*_(lowest)), a maximum change in botha* and b* values, or a maximum change in the quantity√((a*_(highest)−a*_(lowest))²+(b*_(highest)−b*_(lowest))²).

Substrate

The substrate 110 may include an inorganic material and may include anamorphous substrate, a crystalline substrate or a combination thereof.The substrate 110 may be formed from man-made materials and/or naturallyoccurring materials (e.g., quartz and polymers). For example, in someinstances, the substrate 110 may be characterized as organic and mayspecifically be polymeric. Examples of suitable polymers include,without limitation: thermoplastics including polystyrene (PS) (includingstyrene copolymers and blends), polycarbonate (PC) (including copolymersand blends), polyesters (including copolymers and blends, includingpolyethyleneterephthalate and polyethyleneterephthalate copolymers),polyolefins (PO) and cyclicpolyolefins (cyclic-PO), polyvinylchloride(PVC), acrylic polymers including polymethyl methacrylate (PMMA)(including copolymers and blends), thermoplastic urethanes (TPU),polyetherimide (PEI) and blends of these polymers with each other. Otherexemplary polymers include epoxy, styrenic, phenolic, melamine, andsilicone resins.

In some specific embodiments, the substrate 110 may specifically excludepolymeric, plastic and/or metal substrates. The substrate may becharacterized as alkali-including substrates (i.e., the substrateincludes one or more alkalis). In one or more embodiments, the substrateexhibits a refractive index in the range from about 1.45 to about 1.55.In specific embodiments, the substrate 110 may exhibit an averagestrain-to-failure at a surface on one or more opposing major surfacethat is 0.5% or greater, 0.6% or greater, 0.7% or greater, 0.8% orgreater, 0.9% or greater, 1% or greater, 1.1% or greater, 1.2% orgreater, 1.3% or greater, 1.4% or greater 1.5% or greater or even 2% orgreater, as measured using ball-on-ring testing using at least 5, atleast 10, at least 15, or at least 20 samples. In specific embodiments,the substrate 110 may exhibit an average strain-to-failure at itssurface on one or more opposing major surface of about 1.2%, about 1.4%,about 1.6%, about 1.8%, about 2.2%, about 2.4%, about 2.6%, about 2.8%,or about 3% or greater.

Suitable substrates 110 may exhibit an elastic modulus (or Young'smodulus) in the range from about 30 GPa to about 120 GPa. In someinstances, the elastic modulus of the substrate may be in the range fromabout 30 GPa to about 110 GPa, from about 30 GPa to about 100 GPa, fromabout 30 GPa to about 90 GPa, from about 30 GPa to about 80 GPa, fromabout 30 GPa to about 70 GPa, from about 40 GPa to about 120 GPa, fromabout 50 GPa to about 120 GPa, from about 60 GPa to about 120 GPa, fromabout 70 GPa to about 120 GPa, and all ranges and sub-rangestherebetween.

In one or more embodiments, the amorphous substrate may include glass,which may be strengthened or non-strengthened. Examples of suitableglass include soda lime glass, alkali aluminosilicate glass, alkalicontaining borosilicate glass and alkali aluminoborosilicate glass. Insome variants, the glass may be free of lithia. In one or morealternative embodiments, the substrate 110 may include crystallinesubstrates such as glass ceramic substrates (which may be strengthenedor non-strengthened) or may include a single crystal structure, such assapphire. In one or more specific embodiments, the substrate 110includes an amorphous base (e.g., glass) and a crystalline cladding(e.g., sapphire layer, a polycrystalline alumina layer and/or or aspinel (MgAl₂O₄) layer).

The substrate 110 of one or more embodiments may have a hardness that isless than the hardness of the article (as measured by the BerkovichIndenter Hardness Test described herein). The hardness of the substratemay be measured using known methods in the art, including but notlimited to the Berkovich Indenter Hardness Test or Vickers hardnesstest.

The substrate 110 may be substantially planar or sheet-like, althoughother embodiments may utilize a curved or otherwise shaped or sculptedsubstrate. The substrate 110 may be substantially optically clear,transparent and free from light scattering. In such embodiments, thesubstrate may exhibit an average light transmission over the opticalwavelength regime of about 85% or greater, about 86% or greater, about87% or greater, about 88% or greater, about 89% or greater, about 90% orgreater, about 91% or greater or about 92% or greater. In one or morealternative embodiments, the substrate 110 may be opaque or exhibit anaverage light transmission over the optical wavelength regime of lessthan about 10%, less than about 9%, less than about 8%, less than about7%, less than about 6%, less than about 5%, less than about 4%, lessthan about 3%, less than about 2%, less than about 1%, or less thanabout 0%. In some embodiments, these light reflectance and transmittancevalues may be a total reflectance or total transmittance (taking intoaccount reflectance or transmittance on both major surfaces of thesubstrate) or may be observed on a single side of the substrate (i.e.,on the anti-reflective surface 122 only, without taking into account theopposite surface). Unless otherwise specified, the average reflectanceor transmittance is measured at an incident illumination angle of 0degrees (however, such measurements may be provided at incidentillumination angles of 45 degrees or 60 degrees). The substrate 110 mayoptionally exhibit a color, such as white, black, red, blue, green,yellow, orange etc.

Additionally or alternatively, the physical thickness of the substrate110 may vary along one or more of its dimensions for aesthetic and/orfunctional reasons. For example, the edges of the substrate 110 may bethicker as compared to more central regions of the substrate 110. Thelength, width and physical thickness dimensions of the substrate 110 mayalso vary according to the application or use of the article 100.

The substrate 110 may be provided using a variety of differentprocesses. For instance, where the substrate 110 includes an amorphoussubstrate such as glass, various forming methods can include float glassprocesses and down-draw processes such as fusion draw and slot draw.

Once formed, a substrate 110 may be strengthened to form a strengthenedsubstrate. As used herein, the term “strengthened substrate” may referto a substrate that has been chemically strengthened, for examplethrough ion-exchange of larger ions for smaller ions in the surface ofthe substrate. However, other strengthening methods known in the art,such as thermal tempering, or utilizing a mismatch of the coefficient ofthermal expansion between portions of the substrate to createcompressive stress and central tension regions, may be utilized to formstrengthened substrates.

Where the substrate is chemically strengthened by an ion exchangeprocess, the ions in the surface layer of the substrate are replacedby—or exchanged with—larger ions having the same valence or oxidationstate. Ion exchange processes are typically carried out by immersing asubstrate in a molten salt bath containing the larger ions to beexchanged with the smaller ions in the substrate. It will be appreciatedby those skilled in the art that parameters for the ion exchangeprocess, including, but not limited to, bath composition andtemperature, immersion time, the number of immersions of the substratein a salt bath (or baths), use of multiple salt baths, additional stepssuch as annealing, washing, and the like, are generally determined bythe composition of the substrate and the desired compressive stress(CS), depth of compressive stress layer (or depth of layer) of thesubstrate that result from the strengthening operation. By way ofexample, ion exchange of alkali metal-containing glass substrates may beachieved by immersion in at least one molten bath containing a salt suchas, but not limited to, nitrates, sulfates, and chlorides of the largeralkali metal ion. The temperature of the molten salt bath typically isin a range from about 380° C. up to about 450° C., while immersion timesrange from about 15 minutes up to about 40 hours. However, temperaturesand immersion times different from those described above may also beused.

In addition, non-limiting examples of ion exchange processes in whichglass substrates are immersed in multiple ion exchange baths, withwashing and/or annealing steps between immersions, are described in U.S.patent application Ser. No. 12/500,650, filed Jul. 10, 2009, by DouglasC. Allan et al., entitled “Glass with Compressive Surface for ConsumerApplications” and claiming priority from U.S. Provisional PatentApplication No. 61/079,995, filed Jul. 11, 2008, in which glasssubstrates are strengthened by immersion in multiple, successive, ionexchange treatments in salt baths of different concentrations; and U.S.Pat. No. 8,312,739, by Christopher M. Lee et al., issued on Nov. 20,2012, and entitled “Dual Stage Ion Exchange for Chemical Strengtheningof Glass,” and claiming priority from U.S. Provisional PatentApplication No. 61/084,398, filed Jul. 29, 2008, in which glasssubstrates are strengthened by ion exchange in a first bath is dilutedwith an effluent ion, followed by immersion in a second bath having asmaller concentration of the effluent ion than the first bath. Thecontents of U.S. patent application Ser. No. 12/500,650 and U.S. Pat.No. 8,312,739 are incorporated herein by reference in their entirety.

The degree of chemical strengthening achieved by ion exchange may bequantified based on the parameters of central tension (CT), surface CS,and depth of layer (DOL). Surface CS may be measured near the surface orwithin the strengthened glass at various depths. A maximum CS value mayinclude the measured CS at the surface (CS_(s)) of the strengthenedsubstrate. The CT, which is computed for the inner region adjacent thecompressive stress layer within a glass substrate, can be calculatedfrom the CS, the physical thickness t, and the DOL. CS and DOL aremeasured using those means known in the art. Such means include, but arenot limited to, measurement of surface stress (FSM) using commerciallyavailable instruments such as the FSM-6000, manufactured by Luceo Co.,Ltd. (Tokyo, Japan), or the like, and methods of measuring CS and DOLare described in ASTM 1422C-99, entitled “Standard Specification forChemically Strengthened Flat Glass,” and ASTM 1279.19779 “Standard TestMethod for Non-Destructive Photoelastic Measurement of Edge and SurfaceStresses in Annealed, Heat-Strengthened, and Fully-Tempered Flat Glass,”the contents of which are incorporated herein by reference in theirentirety. Surface stress measurements rely upon the accurate measurementof the stress optical coefficient (SOC), which is related to thebirefringence of the glass substrate. SOC in turn is measured by thosemethods that are known in the art, such as fiber and four point bendmethods, both of which are described in ASTM standard C770-98 (2008),entitled “Standard Test Method for Measurement of Glass Stress-OpticalCoefficient,” the contents of which are incorporated herein by referencein their entirety, and a bulk cylinder method. The relationship betweenCS and CT is given by the expression (1):

CT=(CS·DOL)/(t−2 DOL)   (1),

wherein t is the physical thickness (μm) of the glass article. Invarious sections of the disclosure, CT and CS are expressed herein inmegaPascals (MPa), physical thickness t is expressed in eithermicrometers (μm) or millimeters (mm) and DOL is expressed in micrometers(μm).

In one embodiment, a strengthened substrate 110 can have a surface CS of250 MPa or greater, 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater. The strengthened substrate may have a DOL of 10 μmor greater, 15 μm or greater, 20 μm or greater (e.g., 25 μm, 30 μm, 35μm, 40 μm, 45 μm, 50 μm or greater) and/or a CT of 10 MPa or greater, 20MPa or greater, 30 MPa or greater, 40 MPa or greater (e.g., 42 MPa, 45MPa, or 50 MPa or greater) but less than 100 MPa (e.g., 95, 90, 85, 80,75, 70, 65, 60, 55 MPa or less). In one or more specific embodiments,the strengthened substrate has one or more of the following: a surfaceCS greater than 500 MPa, a DOL greater than 15 μm, and a CT greater than18 MPa.

Example glasses that may be used in the substrate may include alkalialuminosilicate glass compositions or alkali aluminoborosilicate glasscompositions, though other glass compositions are contemplated. Suchglass compositions are capable of being chemically strengthened by anion exchange process. One example glass composition comprises SiO₂, B₂O₃and Na₂O, where (SiO₂+B₂O₃)≧66 mol. %, and Na₂O≧9 mol. %. In anembodiment, the glass composition includes at least 6 wt. % aluminumoxide. In a further embodiment, the substrate includes a glasscomposition with one or more alkaline earth oxides, such that a contentof alkaline earth oxides is at least 5 wt. %. Suitable glasscompositions, in some embodiments, further comprise at least one of K₂O,MgO, and CaO. In a particular embodiment, the glass compositions used inthe substrate can comprise 61-75 mol. % SiO2; 7-15 mol. % Al₂O₃; 0-12mol. % B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. % MgO; and 0-3mol. % CaO.

A further example glass composition suitable for the substratecomprises: 60-70 mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15mol. % Li₂O; 0-20 mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10mol. % CaO; 0-5 mol. % ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 12 mol.%≦(Li₂O+Na₂O+K₂O)≦20 mol. % and 0 mol. %≦(MgO+CaO)≦10 mol. %.

A still further example glass composition suitable for the substratecomprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≦(Li₂O+Na₂O+K₂O)≦18 mol. % and 2 mol. %≦(MgO+CaO)≦7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass compositionsuitable for the substrate comprises alumina, at least one alkali metaland, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments at least 58 mol. % SiO₂, and in still other embodiments atleast 60 mol. % SiO₂, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e.,sum of modifiers) is greater than 1, where in the ratio the componentsare expressed in mol. % and the modifiers are alkali metal oxides. Thisglass composition, in particular embodiments, comprises: 58-72 mol. %SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol. % B₂O₃; 8-16 mol. % Na₂O; and 0-4mol. % K₂O, wherein the ratio (Al₂O₃+B₂O₃)/Σmodifiers (i.e., sum ofmodifiers) is greater than 1.

In still another embodiment, the substrate may include an alkalialuminosilicate glass composition comprising: 64-68 mol. % SiO₂; 12-16mol. % Na₂O; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol. %≦SiO₂+B₂O₃+CaO≦69 mol.%; Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≦MgO+CaO+SrO≦8 mol. %;(Na₂O+B₂O₃)−Al₂O₃≦2 mol. %; 2 mol. %≦Na₂O−Al₂O₃≦6 mol. %; and 4 mol.%≦(Na₂O+K₂O)−Al₂O₃≦10 mol. %.

In an alternative embodiment, the substrate may comprise an alkalialuminosilicate glass composition comprising: 2 mol % or more of Al₂O₃and/or ZrO₂, or 4 mol % or more of Al₂O₃ and/or ZrO₂.

Where the substrate 110 includes a crystalline substrate, the substratemay include a single crystal, which may include Al₂O₃. Such singlecrystal substrates are referred to as sapphire. Other suitable materialsfor a crystalline substrate include polycrystalline alumina layer and/orspinel (MgAl₂O₄).

Optionally, the crystalline substrate 110 may include a glass ceramicsubstrate, which may be strengthened or non-strengthened. Examples ofsuitable glass ceramics may include Li₂O—Al₂O₃—SiO₂ system (i.e.LAS-System) glass ceramics, MgO—Al₂O₃—SiO₂ system (i.e. MAS-System)glass ceramics, and/or glass ceramics that include a predominant crystalphase including β-quartz solid solution, β-spodumene ss, cordierite, andlithium disilicate. The glass ceramic substrates may be strengthenedusing the chemical strengthening processes disclosed herein. In one ormore embodiments, MAS-System glass ceramic substrates may bestrengthened in Li₂SO₄ molten salt, whereby an exchange of 2Li⁺ for Mg²⁺can occur.

The substrate 110 according to one or more embodiments can have aphysical thickness ranging from about 100 μm to about 5 mm. Examplesubstrate 110 physical thicknesses range from about 100 μm to about 500μm (e.g., 100, 200, 300, 400 or 500 μm). Further example substrate 110physical thicknesses range from about 500 μm to about 1000 μm (e.g.,500, 600, 700, 800, 900 or 1000 μm). The substrate 110 may have aphysical thickness greater than about 1 mm (e.g., about 2, 3, 4, or 5mm). In one or more specific embodiments, the substrate 110 may have aphysical thickness of 2 mm or less or less than 1 mm. The substrate 110may be acid polished or otherwise treated to remove or reduce the effectof surface flaws.

Anti-Reflective Coating

As shown in FIG. 1, the anti-reflective coating 130 may include aplurality of layers such that one or more layers may be disposed on theopposite side of the substrate 110 from the anti-reflective coating 130(i.e., on major surface 114) (shown in FIG. 1).

The physical thickness of the anti-reflective coating 130 disposed onthe major surface 114 may be in the range from about 0.1 μm to about 5μm. In some instances, the physical thickness of the anti-reflectivecoating 140 disposed on major surface 114 may be in the range from about0.01 μm to about 0.9 μm, from about 0.01 μm to about 0.8 μm, from about0.01 μm to about 0.7 μm, from about 0.01 μm to about 0.6 μm, from about0.01 μm to about 0.5 μm, from about 0.01 μm to about 0.4 μm, from about0.01 μm to about 0.3 μm, from about 0.01 μm to about 0.2 μm, from about0.01 μm to about 0.1 μm, from about 0.02 μm to about 1 μm, from about0.03 μm to about 1 μm, from about 0.04 μm to about 1 μm, from about 0.05μm to about 1 μm, from about 0.06 μm to about 1 μm, from about 0.07 μmto about 1 μm, from about 0.08 μm to about 1 μm, from about 0.09 μm toabout 1 μm, from about 0.2 μm to about 1 μm, from about 0.3 μm to about5 μm, from about 0.4 μm to about 3 μm, from about 0.5 μm to about 3 μm,from about 0.6 μm to about 2 μm, from about 0.7 μm to about 1 μm, fromabout 0.8 μm to about 1 μm, or from about 0.9 μm to about 1 μm, and allranges and sub-ranges therebetween.

The articles 100 disclosed herein may be incorporated into anotherarticle such as an article with a display (or display articles) (e.g.,consumer electronics, including mobile phones, tablets, computers,navigation systems, and the like), architectural articles,transportation articles (e.g., automotive, trains, aircraft, sea craft,etc.), appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof. An exemplary article incorporating any one of articles 100 isshown in FIGS. 54A and 54B. Specifically, FIGS. 54A and 54B show aconsumer electronic device 5100 including a housing 5102 having front5104, back 5106, and side surfaces 5108; electrical components (notshown) that are at least partially inside or entirely within the housingand including at least a controller, a memory, and a display 5110 at oradjacent to the front surface of the housing; and a cover substrate 5112at or over the front surface of the housing such that it is over thedisplay. In some embodiments, the cover substrate 5112 may include anyone of articles 100 disclosed herein.

A second aspect of this disclosure pertains to a method for forming thearticles described herein. In one embodiment, the method includesproviding a substrate having a major surface in a coating chamber,forming a vacuum in the coating chamber, forming a durable opticalcoating as described herein on the major surface, optionally forming anadditional coating comprising at least one of an easy-to-clean coatingand a scratch resistant coating, on the optical coating, and removingthe substrate from the coating chamber. In one or more embodiments, theoptical coating and the additional coating are formed in either the samecoating chamber or without breaking vacuum in separate coating chambers.

In one or more embodiments, the method may include loading the substrateon carriers which are then used to move the substrate in and out ofdifferent coating chambers, under load lock conditions so that a vacuumis preserved as the substrate is moved.

The optical coating 120 and/or the additional coating 140 may be formedusing various deposition methods such as vacuum deposition techniques,for example, chemical vapor deposition (e.g., plasma enhanced chemicalvapor deposition (PECVD), low-pressure chemical vapor deposition,atmospheric pressure chemical vapor deposition, and plasma-enhancedatmospheric pressure chemical vapor deposition), physical vapordeposition (e.g., reactive or nonreactive sputtering or laser ablation),thermal or e-beam evaporation and/or atomic layer deposition.Liquid-based methods may also be used such as spraying, dipping, spincoating, or slot coating (for example, using sol-gel materials). Wherevacuum deposition is utilized, inline processes may be used to form theoptical coating 120 and/or the additional coating 140 in one depositionrun. In some instances, the vacuum deposition can be made by a linearPECVD source.

In some embodiments, the method may include controlling the thickness ofthe optical coating 120 and/or the additional coating 140 so that itdoes not vary by more than about 4% along at least about 80% of the areaof the anti-reflective surface 122 or from the target thickness for eachlayer at any point along the substrate area. In some embodiments, thethickness of the optical coating 120 and/or the additional coating 140so that it does not vary by more than about 4% along at least about 95%of the area of the anti-reflective surface 122.

EXAMPLES

Various embodiments will be further clarified by the following examples.In the Examples, it should be noted that AlO_(x)N_(y) andSi_(u)Al_(v)O_(x)N_(y) were found to be substantially interchangeable asthe high-index material in the modeled examples, with only minor processadjustments necessary to re-create the targeted refractive indexdispersion values and layer thickness designs provided, which areapparent to one of ordinary skill in the art. In addition, for each ofthe examples, an optional capping layer can be added, with a preferredcapping layer being a low-friction, hydrophobic, or easy-to-cleancoating or surface treatment, such as a diamond-like carbon, silane(e.g. fluorosilane), phosphonate, alkene, or alkyne. In someembodiments, these coatings or surface treatments can be added directlyon the top surface of the examples as listed below. In some embodiments,the top-most (air side) layer of the examples as described below can betruncated or reduced in thickness to account for the optical effect ofthe capping layer, which may comprise a finite thickness of about 0.5-30nm and an effective refractive index of 1.3-1.7. In examples, thethickness of the thickest (scratch resistant) layer is sometimes listedas a range. The coating is designed to be optically robust to changes inthe thickness of the thickest layer, which can be adjusted to optimizetrade-offs between various parameters such as cost, coating time, andhardness or scratch resistance.

Modeled Examples 1-12

Modeled Examples 1-12 used modeling to demonstrate the reflectancespectra of articles that included embodiments of a durable andscratch-resistant optical coating, as described herein. In ModeledExamples 1-12 the optical coating included AlO_(x)N_(y) and SiO₂ layers,and a strengthened aluminosilicate glass substrate having a nominalcomposition of about 58 mol % SiO₂, 17 mol % Al₂O₃, 17 mol % Na₂O, 3 mol% MgO, 0.1 mol % SnO, and 6.5 mol % P₂O₅, as shown in Tables 1-12.

To determine the refractive index dispersion curves for the coatingmaterials, layers of each coating material were formed onto siliconwafers by DC, RF or RF superimposed DC reactive sputtering from asilicon, aluminum, silicon and aluminum combined or co-sputtered, ormagnesium fluoride target (respectively) at a temperature of about 50°C. using ion assist. The wafer was heated to 200° C. during depositionof some layers and targets having a 3 inch diameter were used. Reactivegases used included nitrogen, fluorine and oxygen; argon was used as theinert gas. The RF power was supplied to the silicon target at 13.56 Mhzand DC power was supplied to the Si target, Al target and other targets.

The refractive indices (as a function of wavelength) of each of theformed layers and the glass substrate were measured using spectroscopicellipsometry. The refractive indices thus measured were then used tocalculate reflectance spectra for Modeled Examples 2-5. The modeledexamples use a single refractive index value in their descriptive tablesfor convenience, which corresponds to a point selected from thedispersion curves at about 550 nm wavelength.

TABLE 1 Structure of Modeled Example 1. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical 1 AlO_(x)N_(y) 2.00605 32 coating SiO₂1.48114 12 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant (may be in rangefrom Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78 AlO_(x)N_(y) 2.00605 44.19 2SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.00605 24.3 3 SiO₂ 1.48114 58.55AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542 Total coating thickness(nm) 2219.7

TABLE 2 Structure of Modeled Example 2. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 45 coating 1 AlO_(x)N_(y)2.00605 45 SiO₂ 1.48114 10 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant(may be in range from Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2275.7

TABLE 3 Structure of Modeled Example 3. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 10 coating 1 AlO_(x)N_(y)2.00605 30 SiO₂ 1.48114 10 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant(may be in range from Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2225.7

TABLE 4 Structure of Modeled Example 4. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 30 coating 1 AlO_(x)N_(y)2.00605 47 SiO₂ 1.48114 5 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant(may be in range from Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2257.7

TABLE 5 Structure of Modeled Example 5. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 2 coating 1 AlO_(x)N_(y)2.00605 25 SiO₂ 1.48114 25 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant(may be in range from Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2227.7

TABLE 6 Structure of Modeled Example 6. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical 1 AlO_(x)N_(y) 2.00605 25 coating SiO₂1.48114 25 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant (may be in rangefrom Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78 AlO_(x)N_(y) 2.00605 44.19 2SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.00605 24.3 3 SiO₂ 1.48114 58.55AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542 Total coating thickness(nm) 2225.7

TABLE 7 Structure of Modeled Example 7. Refractive Coating/ Periods, ifIndex (at Layer applicable Material 550 nm) Physical Thickness (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 20 coating 1 AlO_(x)N_(y)2.00605 24 SiO₂ 1.48114 18 Scratch- AlO_(x)N_(y) 2.00605 2000 Resistant(may be in range from Layer 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2237.7

TABLE 8 Structure of Modeled Example 8. Refractive Physical Coating/Periods, if Index Thickness Layer applicable Material (at 550 nm) (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 40 coating 1 AlO_(x)N_(y)2.00605 22 SiO₂ 1.48114 18 Scratch- AlO_(x)N_(y) 2.00605 2000 (mayResistant be in Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2255.7

TABLE 9 Structure of Modeled Example 9. Refractive Physical Coating/Periods, if Index Thickness Layer applicable Material (at 550 nm) (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 75 coating 1 AlO_(x)N_(y)2.00605 27 SiO₂ 1.48114 16 Scratch- AlO_(x)N_(y) 2.00605 2000 (mayResistant be in Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2239.7

TABLE 10 Structure of Modeled Example 10. Refractive Physical Coating/Periods, if Index Thickness Layer applicable Material (at 550 nm) (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 100 coating 1 AlO_(x)N_(y)2.00605 34 SiO₂ 1.48114 15 Scratch- AlO_(x)N_(y) 2.00605 2000 (mayResistant be in Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2324.7

TABLE 11 Structure of Modeled Example 11. Refractive Physical Coating/Periods, if Index Thickness Layer applicable Material (at 550 nm) (nm)Ambient — Air 1 medium Optical 1 AlO_(x)N_(y) 2.00605 18 coating SiO₂1.48114 50 Scratch- AlO_(x)N_(y) 2.00605 2000 (may Resistant be in Layerrange from 100-5000 nm) 1 SiO₂ 1.48114 8.78 AlO_(x)N_(y) 2.00605 44.19 2SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.00605 24.3 3 SiO₂ 1.48114 58.55AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542 Total coating thickness(nm) 2243.7

TABLE 12 Structure of Modeled Example 12. Refractive Physical Coating/Periods, if Index Thickness Layer applicable Material (at 550 nm) (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 60 coating 1 AlO_(x)N_(y)2.00605 34 SiO₂ 1.48114 15.5 Scratch- AlO_(x)N_(y) 2.00605 2000 (mayResistant be in Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.78AlO_(x)N_(y) 2.00605 44.19 2 SiO₂ 1.48114 32.41 AlO_(x)N_(y) 2.0060524.3 3 SiO₂ 1.48114 58.55 AlO_(x)N_(y) 2.00605 7.47 — — AS Glass 1.50542Total coating thickness (nm) 2293.7

FIGS. 10-33 show the reflectance spectrum for viewing angles ofincidence of 8°, 20°, 40°, and 60° and reflected color for angles from0°-60° for D65 and F2 illumination. FIGS. 10-11 show the calculatedreflectance spectra and the calculated reflected color, respectively,for only the anti-reflective surface of Modeled Example 1. FIGS. 12-13show the calculated reflectance spectra and the calculated reflectedcolor, respectively, for only the anti-reflective surface of ModeledExample 2. FIGS. 14-15 show the calculated reflectance spectra and thecalculated reflected color, respectively, for only the anti-reflectivesurface of Modeled Example 3. FIGS. 16-17 show the calculatedreflectance spectra and the calculated reflected color, respectively,for only the anti-reflective surface of Modeled Example 4. FIGS. 18-19show the calculated reflectance spectra and the calculated reflectedcolor, respectively, for only the anti-reflective surface of ModeledExample 5. FIGS. 20-21 show the calculated reflectance spectra and thecalculated reflected color, respectively, for only the anti-reflectivesurface of Modeled Example 6. FIGS. 22-23 show the calculatedreflectance spectra and the calculated reflected color, respectively,for only the anti-reflective surface of Modeled Example 7. FIGS. 24-25show the calculated reflectance spectra and the calculated reflectedcolor, respectively, for only the anti-reflective surface of ModeledExample 8. FIGS. 26-27 show the calculated reflectance spectra and thecalculated reflected color, respectively, for only the anti-reflectivesurface of Modeled Example 9. FIGS. 28-29 show the calculatedreflectance spectra and the calculated reflected color, respectively,for only the anti-reflective surface of Modeled Example 10. FIGS. 30-31show the calculated reflectance spectra and the calculated reflectedcolor, respectively, for only the anti-reflective surface of ModeledExample 11. FIGS. 32-33 show the calculated reflectance spectra and thecalculated reflected color, respectively, for only the anti-reflectivesurface of Modeled Example 12.

The optical performance of Modeled Examples 1-12 is summarized in Table13.

TABLE 13 Optical performance of Modeled Examples 1-12. Maximum AmountAnti- angular color Total Amount of high- reflective shift, viewing(sum) of low- Thickness of index surface angles 0-60 index materialtop-most material in reflectance, degrees, D65 or on air-side of (userside) top 500 photopic F2, sample thickest high- low index nm of Modeledaverage (%) referenced to index hard (e.g. SiO₂) coated Example (singleside) itself layer (nm) layer (nm) article (%) 1 7.85 1.1 12 0 97.6 26.45 0.8 55 45 89 3 8.1 1.05 20 10 96 4 8.4 0.6 35 30 93 5 4.9 3.0 27 294.6 6 4.9 2.7 25 0 95 7 5.65 2.4 38 20 92.4 8 4.0 3.75 58 40 88.4 9 2.02.2 91 75 81.8 10 1.3 2.2 115 100 77 11 1.8 17.6 50 0 90 12 4.0 1.2 75.560 84.9

As shown in FIGS. 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, and 32,Modeled Examples 1-12 exhibit low reflectance (i.e., values less thanabout 10% and less than about 8%), for viewing angles of 8°, 20°, and40°, with the reflectance for a viewing angle of 60° being slightlyhigher, over the optical wavelength regime. Modeled Example 10 exhibitedvery low reflectance for viewing angles of 8°, 20°, 40° and 60° (e.g., amaximum average reflectance of about 7% or less). At viewing angles of8°, 20°, and 40°, the average reflectance is even lower (i.e., less thanabout 2%).

As shown in FIGS. 11 and 29, Modeled Examples 1 and 10 exhibited areflected color, at viewing angles from normal incidence to 60°, of lessthan about 2 for both D65 and F2 illuminants. As shown in FIGS. 19 and21, Modeled Example 5 and 6 exhibited a range of reflected color, atviewing angles from normal incidence to 60°, of less than about 3 forboth D65 and F2 illuminants.

The optical coatings of Modeled Examples 5 and 12 (Tables 5 and 12) havea balance of optical and mechanical properties. That is, these examplesbalance scratch resistance with good optical performance in terms ofreflectance, color, and/or color shift. More specifically, theseexamples have a reflectance (over the optical wavelength regime, atangles of incidence of from 8 degrees to about 40 degrees) of about 4%to about 6% (and less than about 10% or about 12% in some examples—angleof incidence of about 60 degrees), and maintain good scratch resistance.Compared to optical coatings optimized for scratch resistance (whichhave a tradeoff of higher reflectance, i.e., about 10%), the coatings inthese examples sacrifice a small amount of scratch resistance todesirably decrease reflectance (to a range of from about 4% to about 6%,and to less than about 10% in some examples). Compared to opticalcoatings optimized for low reflectance (i.e., about 1%, which wouldsacrifice scratch resistance for the low reflectance), the coatings inthese examples sacrifice a small amount of reflectance (i.e.,reflectance in a range of from about 4% to about 6%, and to less thanabout 10% in some examples, versus the about 1% for a coating optimizedfor low reflectance) to desirably increase the scratch resistance. TheseExamples also maintain good optical characteristics in terms oftransmitted/reflected color coordinates (i.e., low color), and low colorshift.

It is believed that Modeled Examples 1-12 also exhibit the hardnessvalues described herein, as measured by the Berkovich Indenter HardnessTest (and, in particular, a hardness in the range from about 14 GPa toabout 21 GPa).

Example 13 and Modeled Example 14

Example 13 and Modeled Example 14 used modeling to demonstrate thereflectance spectra of articles that included embodiments of a durableand scratch-resistant optical coating, as described herein. Also, theoptical coating of Example 13 was fabricated and tested. In Example 13and Modeled Example 14 the optical coating included AlO_(x)N_(y) andSiO₂ layers, and a strengthened aluminosilicate glass substrate having anominal composition of about 58 mol % SiO₂, 17 mol % Al₂O₃, 17 mol %Na₂O, 3 mol % MgO, 0.1 mol % SnO, and 6.5 mol % P₂O₅, prior to ionexchange with a K₂O bath, as shown in Tables 13 and 14. Refractive indexdispersion curves for coating materials and substrate used for Example13 and Modeled Example 14 were obtained in a similar manner as ModeledExamples 1-12.

TABLE 14 Structure of Example 13 Refractive Physical Coating/ Periods,if Index Thickness Layer applicable Material (at 550 nm) (nm) Ambient —Air 1 medium Optical SiO₂ 1.48114 60 coating 1 AlO_(x)N_(y) 2.00605 34SiO₂ 1.48114 15.5 Scratch- AlO_(x)N_(y) 2.00605 2000 (may Resistant bein Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.93 AlO_(x)N_(y)2.00605 42.63 2 SiO₂ 1.48114 30.12 AlO_(x)N_(y) 2.00605 24.48 3 SiO₂1.48114 52.41 AlO_(x)N_(y) 2.00605 7.7 — — AS Glass 1.50542 Totalcoating thickness (nm) 2275.77

TABLE 15 Structure of Modeled Example 14. Refractive Physical Coating/Periods, if Index Thickness Layer applicable Material (at 550 nm) (nm)Ambient — Air 1 medium Optical SiO₂ 1.48114 10 coating 1 AlO_(x)N_(y)2.00605 25 SiO₂ 1.48114 25 Scratch- AlO_(x)N_(y) 2.00605 2000 (mayResistant be in Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.93AlO_(x)N_(y) 2.00605 42.63 2 SiO₂ 1.48114 30.12 AlO_(x)N_(y) 2.0060524.48 3 SiO₂ 1.48114 52.41 AlO_(x)N_(y) 2.00605 7.7 — — AS Glass 1.50542Total coating thickness (nm) 2226.27

The optical coating of Example 13 had a reflected D65 color of a* equalto about 0.05 and b* equal to about −1.7 and had a transmitted D65 colorof a* equal to about −0.05 and b* equal to about 0.8. Additionally, theoptical coating of Example 13 was fabricated and experimentallyanalyzed. Two samples were fabricated for the optical coating of Example13 (Sample 1 and Sample 2). Sample 1 was tested for reflectance over thevisible wavelength regime at various angles of incidence, which is shownin FIG. 49. The light transmittance of the optical coating of Sample 1is shown in FIGS. 50 and 51, where FIG. 50 shows light transmittanceover a wider range of light wavelengths than FIG. 51. FIGS. 52 and 53depict reflected color and transmitted color for Samples 1 and 2 atspecified angles of incidence, respectively.

FIG. 34 shows the hardness profile (Berkovitch hardness for indentationdepths of from about 0 nm to about 1000 nm for four optical coatings,where the optical coating of Table 13 is shown as 803, the opticalcoating of Table 14 is shown as 802.

Example 15

Optical coatings were prepared that included AlO_(x)N_(y) and SiO₂layers, and following such preparation were subjected to a plasmatreatments, were capped with an SiO₂ layer of 6 nm and a easy to cleancoating comprising 6.4 nm of a fluorosilane material. The opticalcoating prepared is shown in Table 15. The uppermost SiO₂ layer wasdeposited using e-beam PVD (sputtering was implemented in sisterexperiments).

TABLE 16 Structure of Example 15. Refractive Physical Coating/ Periods,if Index Thickness Layer applicable Material (at 550 nm) (nm) Ambient —Air 1 medium fluorsilane 6.4 SiO₂ 1.48114 6 Optical SiO₂ 1.48114 47.3coating 1 AlO_(x)N_(y) 2.00605 32.8 SiO₂ 1.48114 16.6 Scratch-AlO_(x)N_(y) 2.00605 2025.3 (may Resistant be in Layer range from100-5000 nm) 1 SiO₂ 1.48114 10.7 AlO_(x)N_(y) 2.00605 40.8 2 SiO₂1.48114 33.5 AlO_(x)N_(y) 2.00605 22.9 3 SiO₂ 1.48114 54.9 AlO_(x)N_(y)2.00605 7.1 — — AS Glass 1.50542 Total coating thickness (nm) 2304.3

Optical data was simulated and experimentally collected for the opticalcoating of Table 15. The uppermost SiO₂ layer was also changed to 4 nmand 8 nm to experimentally test slight changes in the thickness of theSiO₂ layer which may be present in industrial application of thecoatings. FIG. 35 shows transmittance of the optical coating of Example15 (Table 16), where a simulated model of a 6 nm uppermost SiO₂ layer isdepicted, and the other data points refer to measured transmittance ofthe optical coating of Example 15 (Table 16) where 4 nm, 6 nm, and 8 nmSiO₂ coatings were deposited following a plasma treatment. FIG. 36 shows2-sided reflectance of the optical coating of Example 15 (Table 16),where a simulated model of a 6 nm uppermost SiO₂ layer is depicted, andthe other data points refer to measured reflectance of the opticalcoating of Table 16 where 0 nm (no additional coating), 4 nm, 6 nm, and8 nm SiO₂ coatings were deposited following a plasma treatment. Table 17shows the transmitted color of the optical coatings of Example 15(transmittance shown in FIG. 35), and Table 18 shows the reflected colorof the optical coatings of Example 15 (reflectance shown in FIG. 36).

TABLE 17 Transmitted color Y L a* b* Simulation 91.92 96.79 −0.04 0.51#492 + 4 nm 91.22 96.50 −0.07 0.63 #492 + 6 nm 91.38 96.57 −0.03 0.55#492 + 8 nm 91.47 96.60 −0.01 0.52

TABLE 18 Reflected color Y L a* b* Simulation 7.76 33.47 −0.06 −0.66#492 + 4 nm 8.09 34.16 −0.04 −1.01 #492 + 6 nm 7.69 33.33 −0.07 −0.24#492 + 8 nm 7.27 32.41 −0.08 0.35

FIG. 37 shows modeled and observed transmittance data for the opticalcoating of Example 15. In FIG. 37, 811 corresponds to simulatedtransmittance at 8° viewing angle and 812 corresponds to observedtransmittance at 8° viewing angle. Table 19 shows reflected color datafor the optical coating of Example 15.

TABLE 19 Spectrum Y L* a* b* Transmitted b* 90.9 96.37 −0.08 0.78 (D65,AOI 8°) Reflected  8° 8.45 34.90 0.08 −1.96 b* (F2) 20° 8.55 35.10 0.06−1.76 40° 9.47 36.87 0.30 −1.60 60° 15.15 45.83 0.27 −0.65

The optical coatings of Example 15 (Table 16) have a balance of opticaland mechanical properties. That is, these examples balance scratchresistance with good optical performance in terms of reflectance, color,and/or color shift. More specifically, these examples have a reflectance(over the optical wavelength regime) of about 6% to less than about 10%(and less than about 8% in some examples), and maintain good scratchresistance. Compared to optical coatings optimized for scratchresistance (which have a tradeoff of higher reflectance, i.e., about10%), the coatings in these examples sacrifice a small amount of scratchresistance to desirably decrease reflectance (to a range of from about6% to less than about 10%, and to less than about 8% in some examples).Compared to optical coatings optimized for low reflectance (i.e., about1%, which would sacrifice scratch resistance for the low reflectance),the coatings in this example sacrifice a small amount of reflectance(i.e., in a range of from about 6% to less than about 10%, and to lessthan about 8% in some examples, versus the about 1% for a coatingoptimized for low reflectance) to desirably increase the scratchresistance. These Examples also maintain good optical characteristics interms of transmitted/reflected color coordinates (i.e., low color), andlow color shift.

Examples 15′-17

Examples 15′-17 used modeling and testing to demonstrate the opticalproperties of articles that included embodiments of a durable andscratch-resistant optical coating, as described herein. Also, theoptical coatings in Examples 15′-17 were fabricated and tested. InExamples 15′-17 the optical coating included AlO_(x)N_(y) and SiO₂layers, and a strengthened aluminosilicate glass substrate having anominal composition of about 58 mol % SiO₂, 17 mol % Al₂O₃, 17 mol %Na₂O, 3 mol % MgO, 0.1 mol % SnO, and 6.5 mol % P₂O₅ , prior to ionexchange with a K₂O bath, as shown in Tables 20, 21 and 22. Refractiveindex dispersion curves for coating materials and substrate used forExamples 15′-17 were obtained in a similar manner as Modeled Examples1-12.

TABLE 20 Example 15′ Refractive Physical Coating/ Periods, if IndexThickness Layer applicable Material (at 550 nm) (nm) Ambient — Air 1medium Optical SiO₂ 1.48114 14.0 coating 1 AlO_(x)N_(y) 2.00605 23.0SiO₂ 1.48114 30.0 Scratch- AlO_(x)N_(y) 2.00605 2000.0 (may Resistant bein Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.6 AlO_(x)N_(y) 2.0060544.1 2 SiO₂ 1.48114 29.4 AlO_(x)N_(y) 2.00605 26.0 3 SiO₂ 1.48114 50.2AlO_(x)N_(y) 2.00605 8.6 — — AS Glass 1.50542 Total coating thickness(nm) 2233.9

TABLE 21 Example 16 Refractive Physical Coating/ Periods, if IndexThickness Layer applicable Material (at 550 nm) (nm) Ambient — Air 1medium Optical SiO₂ 1.48114 60.0 coating 1 AlO_(x)N_(y) 2.00605 34.0SiO₂ 1.48114 18.0 Scratch- AlO_(x)N_(y) 2.00605 2000.0 (may Resistant bein Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.6 AlO_(x)N_(y) 2.0060544.1 2 SiO₂ 1.48114 29.4 AlO_(x)N_(y) 2.00605 26.0 3 SiO₂ 1.48114 50.2AlO_(x)N_(y) 2.00605 8.6 — — AS Glass 1.50542 Total coating thickness(nm) 2278.9

TABLE 22 Example 17 Refractive Physical Coating/ Periods, if IndexThickness Layer applicable Material (at 550 nm) (nm) Ambient — Air 1medium Optical SiO₂ 1.48114 105.0 coating 1 AlO_(x)N_(y) 2.00605 32.0SiO₂ 1.48114 16.0 Scratch- AlO_(x)N_(y) 2.00605 2000.0 (may Resistant bein Layer range from 100-5000 nm) 1 SiO₂ 1.48114 8.6 AlO_(x)N_(y) 2.0060544.1 2 SiO₂ 1.48114 29.4 AlO_(x)N_(y) 2.00605 26.0 3 SiO₂ 1.48114 50.2AlO_(x)N_(y) 2.00605 8.6 — — AS Glass 1.50542 Total coating thickness(nm) 2319.9

FIG. 38 depicts transmission for the optical coatings of Tables 20-22based on modeled and observed results, where 815 corresponds to thecoating of Table 20 measured, 816 corresponds to the coating of Table 20modeled, 817 corresponds to the coating of Table 21 measured, 818corresponds to the coating of Table 21 modeled, 819 corresponds to thecoating of Table 22 measured, and 820 corresponds to the coating ofTable 22 modeled. FIG. 39 depicts reflectance for the optical coatingsof Tables 20-22 based on modeled and observed results. FIG. 40 depictscolor reflected and FIG. 41 depicts color transmitted for the opticalcoatings of Tables 20-22 as measured and modeled. FIG. 42 shows modeledreflectance for the optical coating of Table 20, FIG. 43 shows modeledreflectance for the optical coating of Table 21, and FIG. 44 showsmodeled reflectance for the optical coating of Table 22. FIG. 45 showsmeasured reflectance for the optical coating of Table 20, FIG. 46 showsmeasured reflectance for the optical coating of Table 21, and FIG. 47shows measured reflectance for the optical coating of Table 22. Themodeled and measured reflectance were similar. FIG. 48 showsnanohardness measurements for the optical coatings of Tables 20-22,where 870 corresponds to the optical coating of Table 20, 871corresponds to the optical coating of Table 21, and 872 corresponds tothe optical coating of Table 22. As seen from FIG. 48, desirably,hardness quickly increases within the first 100 nm from the surface (upto a value of about 17 to 20 GPa), and is maintained at about the samevalue (about 17 to 20 GPa) as depth increases from 100 nm to about 700nm or about 800 nm, as measured from the surface. Such a hardnessprofile is desirable in reducing damage from scratches, both more severescratch events responsible for more visible scratches, and less severescratch events that might otherwise affect the surface characteristicsof the optical coatings.

The optical coatings of Examples 15′-17 (Tables 20-22) have a balance ofoptical and mechanical properties. That is, these examples balancescratch resistance with good optical performance in terms ofreflectance, color and/or color shift. More specifically, these exampleshave a reflectance (as measured at a angles of incidence over the rangeof from about 8 degrees to about 40 degrees, and in some examples up toabout 60 degrees) of about greater than 1% to about 6% (over the overthe optical wavelength regime), and maintain good scratch resistance.Compared to optical coatings optimized for scratch resistance (whichhave a tradeoff of higher reflectance, i.e., about 10%), the coatings inthese examples sacrifice a small amount of scratch resistance todesirably decrease reflectance (to values in a range of from aboutgreater than 1% to about 6%). Compared to optical coatings optimized forlow reflectance (i.e., about 1% reflectance, which would sacrificescratch resistance for the low reflectance), the coatings in theseexamples sacrifice a small amount of reflectance (i.e., to values fromabout greater than 1% to about 6% versus the about 1% for a coatingoptimized for low reflectance) to desirably increase the scratchresistance.

It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the invention.

What is claimed is:
 1. An article comprising: a substrate having a majorsurface; and an optical coating disposed on the major surface andforming an anti-reflective surface, the optical coating comprising ananti-reflective coating, wherein: the article exhibits a maximumhardness of about 10 GPa or greater as measured on the anti-reflectivesurface by a Berkovich Indenter Hardness Test along an indentation depthof about 100 nm; the article exhibits a single side average lightreflectance measured only at the anti-reflective surface of about 8% orless, when measured at an incident illumination angle from about 0degrees to about 10 degrees, over an optical wavelength regime in therange from about 400 nm to about 800 nm; and the substrate exhibits anaverage light transmission of about 10% or less, when measured at anincident illumination angle from about 0 degrees to about 10 degrees,over an optical wavelength regime in the range from about 400 nm toabout 800 nm.
 2. The article of claim 1, wherein article exhibits asingle side average photopic light reflectance measured only at theanti-reflective surface of about 2% or less, when measured at anincident illumination angle from about 0 degrees to about 10 degrees,over an optical wavelength regime in the range from about 400 nm toabout 800 nm.
 3. The article of claim 1, wherein the article exhibits amaximum hardness of about 12 GPa or greater as measured on theanti-reflective surface by a Berkovich Indenter Hardness Test along anindentation depth of about 100 nm.
 4. The article of claim 1, whereinthe substrate exhibits an average light transmission of about 6% orless, when measured at an incident illumination angle from about 0degrees to about 10 degrees, over an optical wavelength regime in therange from about 400 nm to about 800 nm.
 5. The article of claim 1,wherein the substrate exhibits an average light transmission of about 1%or less, when measured at an incident illumination angle from about 0degrees to about 10 degrees, over an optical wavelength regime in therange from about 400 nm to about 800 nm.
 6. The article of claim 5,wherein the substrate comprises glass-ceramic.
 7. The article of claim6, wherein the substrate is chemically strengthened.
 8. The article ofclaim 6, wherein the substrate comprises a white or black color.
 9. Thearticle of claim 1, wherein the substrate has a thickness from about 0.2mm to about 2.0 mm.
 10. The article of claim 1, further comprising aneasy-to-clean coating disposed on the anti-reflective coating.
 11. Thearticle of claim 1, wherein the article comprises a scratch resistantlayer having a thickness in the range from about 0.5 micrometer to about3 micrometers, and one or more additional layers positioned over thescratch resistant layer.
 12. The article of claim 11, wherein thescratch resistant layer comprises a high RI material, one or more of thelayers positioned over the scratch resistant layer comprises the high RImaterial, and one or more of the layers positioned over the scratchresistant layer comprises a low RI material.
 13. The article of claim 1,wherein the uppermost 500 nm of the optical coating measured from theanti-reflective surface comprises at least one of: less than about 30%of low RI material; and at least about 70% of high RI material.
 14. Thearticle of claim 1, wherein: the article reflectance color coordinatesin the (L*, a*, b*) colorimetry system at normal incidence under anInternational Commission on Illumination illuminant exhibiting areference point color shift of less than about 5 from a reference pointas measured at the anti-reflective surface, the reference pointcomprising at least one of the color coordinates (a*=0, b*=0), the colorcoordinates (a*=−2, b*=−2), and the reflectance color coordinates of thesubstrate, wherein, when the reference point is the color coordinates(a*=0, b*=0), the color shift is defined by√((a*_(article))²+(b*_(article))²), wherein, when the reference point isthe color coordinates (a*=−2, b*=−2), the color shift is defined by√((a*_(article)+2)²+(b*_(article)+2)²), and wherein, when the referencepoint is the color coordinates of the substrate, the color shift isdefined by√((a*_(article)−a*_(substrate))²+(b*_(article)−b*_(substrate))²). 15.The article of claim 1, wherein the article exhibits an angular colorshift, measured in reflection, of about 5 or less at an incidentillumination angle that is 20 degrees or greater, referenced to normalincidence, under an International Commission on Illumination illuminantselected from the group consisting of A series illuminants, B seriesilluminants, C series illuminants, D series illuminants, and F seriesilluminants, wherein angular color shift is calculated using theequation √((a*₂−a*₁)²+(b*₂−b*₁)²), with a*₁, and b*₁ representing thecoordinates of the article when viewed at normal incidence and a*₂, andb*₂ representing the coordinates of the article when viewed at theincident illumination angle.
 16. The article of claim 15, wherein thearticle exhibits an angular color shift, measured in reflection, ofabout 5 or less at all incident illumination angles in the range fromabout 20 degrees to about 60 degrees.
 17. The article of claim 1,wherein the anti-reflective coating comprises a plurality of layers,wherein the plurality of layers comprises a first low RI layer, a secondhigh RI layer, and an optional third layer, and further wherein theanti-reflective coating comprises a plurality of periods such that thefirst low RI layer and the second high RI layer alternate.
 18. Thearticle of claim 1, wherein the anti-reflective coating comprises afirst portion and a second portion, and wherein the scratch resistantlayer is disposed between the first portion and the second portion. 19.The article of claim 1, wherein the optical coating comprises athickness and a plurality of layers comprising a nitride or oxy-nitridematerial, and where the combined thickness of the layers comprising anitride or an oxynitride is 50% or greater of the thickness of theoptical coating.
 20. A device comprising: a housing having front, back,and side surfaces; electrical components that are at least partiallyinside the housing; a display at or adjacent to the front surface of thehousing; and a cover substrate comprising at least a part of thehousing, wherein the cover substrate comprises the article of claim 1.21. An article comprising: a substrate having a major surface; and anoptical coating disposed on the major surface, wherein: the articleexhibits a maximum hardness of about 10 GPa or greater as measured onthe anti-reflective surface by a Berkovich Indenter Hardness Test alongan indentation depth of about 100 nm; the substrate exhibits an averagelight transmission of about 10% or less, when measured at an incidentillumination angle from about 0 degrees to about 10 degrees, over anoptical wavelength regime in the range from about 400 nm to about 800nm; the substrate comprises glass-ceramic; the article reflectance colorcoordinates in the (L*, a*, b*) colorimetry system at normal incidenceunder an International Commission on Illumination illuminant exhibit areference point color shift of less than about 5 from a reference pointas measured at the anti-reflective surface, the reference pointcomprising at least one of the color coordinates (a*=0, b*=0), the colorcoordinates (a*=−2, b*=−2), and the reflectance color coordinates of thesubstrate, wherein, when the reference point is the color coordinates(a*=0, b*=0), the color shift is defined by√((a*_(article))²+(b*_(article))²), wherein, when the reference point isthe color coordinates (a*=−2, b*=−2), the color shift is defined by√((a*_(article)+2)²+(b*_(article)+2)²), and wherein, when the referencepoint is the color coordinates of the substrate, the color shift isdefined by√((a*_(article)−a*_(substrate))²+(b*_(article)−b*_(substrate))²). 22.The article of claim 21, wherein the substrate is chemicallystrengthened.
 23. The article of claim 22, wherein the substratecomprises a white or black color.
 24. The article of claim 21, whereinthe substrate has a thickness from about 0.21mm to about 2.0 mm.
 25. Thearticle of claim 21, further comprising an easy-to-clean coatingdisposed on the optical coating.
 26. The article of claim 21, whereinthe article comprises a scratch resistant layer having a thickness inthe range from about 0.5 micrometer to about 3 micrometers, and one ormore additional layers positioned over the scratch resistant layer. 27.The article of claim 26, wherein the scratch resistant layer comprises ahigh RI material, one or more of the layers positioned over the scratchresistant layer comprises the high RI material, and one or more of thelayers positioned over the scratch resistant layer comprises a low RImaterial.
 28. The article of claim 21, wherein the optical coatingcomprises a first portion and a second portion, and wherein a scratchresistant layer is disposed between the first portion and the secondportion.
 29. The article of claim 21, wherein the optical coatingcomprises a thickness and a plurality of layers comprising a nitride oroxy-nitride material, and where the combined thickness of the layerscomprising a nitride or an oxynitride is 50% or greater of the thicknessof the optical coating.
 30. A device comprising: a housing having front,back, and side surfaces; electrical components that are at leastpartially inside the housing; a display at or adjacent to the frontsurface of the housing; and a cover substrate comprising at least partof the housing, wherein the cover substrate comprises the article ofclaim 21.